CN117191932A - Method and system for testing metal recovery rate of silicon wafer surface - Google Patents
Method and system for testing metal recovery rate of silicon wafer surface Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 168
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 168
- 239000010703 silicon Substances 0.000 title claims abstract description 168
- 229910052751 metal Inorganic materials 0.000 title claims abstract description 143
- 239000002184 metal Substances 0.000 title claims abstract description 143
- 238000011084 recovery Methods 0.000 title claims abstract description 68
- 238000012360 testing method Methods 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 49
- 238000005260 corrosion Methods 0.000 claims abstract description 50
- 230000007797 corrosion Effects 0.000 claims abstract description 50
- 238000000889 atomisation Methods 0.000 claims abstract description 28
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 230000003647 oxidation Effects 0.000 claims abstract description 22
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 22
- 150000002739 metals Chemical class 0.000 claims abstract description 20
- 238000004321 preservation Methods 0.000 claims abstract description 16
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000001816 cooling Methods 0.000 claims abstract description 15
- 239000001301 oxygen Substances 0.000 claims abstract description 15
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 15
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 13
- 239000007788 liquid Substances 0.000 claims description 50
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 42
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 18
- 238000010998 test method Methods 0.000 claims description 14
- 238000000137 annealing Methods 0.000 claims description 12
- 238000005530 etching Methods 0.000 claims description 12
- 238000001514 detection method Methods 0.000 claims description 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 230000001590 oxidative effect Effects 0.000 claims description 8
- 238000005070 sampling Methods 0.000 claims description 8
- 238000009616 inductively coupled plasma Methods 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 4
- 239000003570 air Substances 0.000 claims description 3
- 239000001307 helium Substances 0.000 claims description 3
- 229910052734 helium Inorganic materials 0.000 claims description 3
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims 1
- 229910001882 dioxygen Inorganic materials 0.000 claims 1
- 238000011534 incubation Methods 0.000 claims 1
- 239000011701 zinc Substances 0.000 abstract description 13
- 239000012488 sample solution Substances 0.000 abstract description 7
- 239000010949 copper Substances 0.000 abstract description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 abstract description 5
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 abstract description 5
- 229910052802 copper Inorganic materials 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 239000004065 semiconductor Substances 0.000 abstract description 3
- 235000012431 wafers Nutrition 0.000 description 146
- 239000000523 sample Substances 0.000 description 21
- 238000011109 contamination Methods 0.000 description 14
- 239000000243 solution Substances 0.000 description 12
- 238000004140 cleaning Methods 0.000 description 9
- 238000001095 inductively coupled plasma mass spectrometry Methods 0.000 description 7
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- 239000002245 particle Substances 0.000 description 3
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
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- 229910052723 transition metal Inorganic materials 0.000 description 2
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- 229910017709 Ni Co Inorganic materials 0.000 description 1
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- 239000002994 raw material Substances 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
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- 238000009279 wet oxidation reaction Methods 0.000 description 1
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Abstract
The invention relates to the technical field of semiconductors, in particular to a method and a system for testing metal recovery rate of a silicon wafer surface. The testing method comprises the following steps: placing the silicon wafer to be tested in an environment of 800-1200 ℃, introducing oxygen containing water vapor for oxidation, cooling to 150-600 ℃ and preserving heat; carrying out atomization corrosion on the silicon wafer to be tested; dropwise adding the corrosion solution on a silicon wafer to be tested which is horizontally placed to obtain a sample solution; and detecting and calculating the metal recovery rate. According to the method for testing the metal recovery rate of the surface of the silicon wafer, the oxide layer is arranged on the surface of the silicon wafer, so that the metal which is transited to the surface of the silicon wafer in the heat preservation stage is enriched in the interface state formed by the oxide layer, the metal content of the silicon wafer can be truly tested, and particularly the content of metals such as copper, zinc and the like with high mobility is tested, and the production process is effectively guided.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a method and a system for testing metal recovery rate of a silicon wafer surface.
Background
Semiconductor wafers are the primary substrate material for modern very large scale integrated circuits and are typically manufactured by processes such as crystal pulling, slicing, chamfering, grinding (including grinding and lapping), etching, polishing, cleaning and inspection. Key parameters affecting the quality of the wafer are mainly geometrical parameters, surface particles and surface metal contamination levels, wherein the surface metal contamination levels influence many factors such as the level of the cleaning machine, the purity of the chemical liquid, the cleaning process, the personnel operation and the environmental conditions.
In the process of processing the silicon wafer, each procedure needs to clean the surface of the silicon wafer to remove abrasive residues and metal contamination left by the previous processing technology. The current processing generally adopts the processes of polishing, pre-cleaning, geometric parameter testing, final cleaning and particle metal testing, and the final cleaning is carried out after the geometric parameter testing, so that the particles and metal contamination of the silicon wafer in the testing process can be ensured to be removed before leaving the factory, and the metal contamination is generally controlled to be less than 10E8 atom/cm 2 Is a level of (c). In the actual silicon wafer surface metal testing process, because metals such as copper, zinc and the like in vivo are more active, the metals can migrate to the surface of the silicon wafer in the standing process, and the subsurface metal recovery rate is low, the silicon wafer surface metal testing result cannot truly reflect the metal contamination level of the silicon wafer.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method and a system for testing the metal recovery rate of the surface of a silicon wafer.
The invention provides a method for testing the recovery rate of metal on the surface of a silicon wafer, which comprises the following steps:
s1, placing a silicon wafer to be tested in an environment of 800-1200 ℃, introducing oxygen containing water vapor for oxidation, and forming an oxide layer on the surface of the silicon wafer to be tested;
s2, cooling to 150-600 ℃ and preserving heat;
s3, carrying out atomization corrosion on the silicon wafer to be tested, and removing an oxide layer;
s4, dropwise adding the corrosion liquid on the silicon wafer to be tested which is horizontally placed, and collecting the corrosion liquid after corroding the silicon wafer to be tested to obtain a sample liquid; repeating 3-n times, wherein n is more than or equal to 3 and less than or equal to 10, and obtaining at least 3 sample liquids;
s5, detecting the concentrations C1, C2, … … and Cn of different metals in each sample liquid, and calculating different metal recovery rates through the following formula:
metal recovery = C1/(c1+c2+ … … +cn) ×100%.
Optionally, the silicon wafer surface metal is selected from one or more of Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
Optionally, in S1, the oxidation time is 30 minutes to 3 hours.
Optionally, in S1, the flow rate of oxygen containing water vapor is 0.1 mL/min-20L/min.
Optionally, in S2, nitrogen, helium or air is introduced during the heat preservation; the heat preservation time is 30 minutes to 2 hours.
Optionally, in S3, atomizing and corroding is performed by adopting a hydrofluoric acid solution, wherein the concentration of the hydrofluoric acid solution is 1% -50% by mass.
Optionally, in S4, the composition of the etching solution is hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70.
alternatively, in S5, the detection is performed using an inductively coupled plasma mass spectrometer.
The invention provides a system for testing the metal recovery rate of the surface of a silicon wafer, which applies the method for testing the metal recovery rate of the surface of the silicon wafer according to the first aspect, and comprises a high-temperature annealing module, an atomization corrosion module, a sampling module and a detection statistics module;
the high-temperature annealing module is used for oxidizing the silicon wafer to be tested at high temperature, cooling and preserving heat;
the atomization corrosion module is used for performing atomization corrosion on the silicon wafer to be tested;
the sampling module is used for dripping the corrosion liquid on the silicon wafer to be tested to obtain a sample liquid;
the detection statistical module is used for detecting the content of different metals in each sample liquid and calculating the recovery rate of the different metals.
Compared with the prior art, the technical scheme provided by the embodiment of the invention has the following advantages:
according to the method for testing the metal recovery rate of the surface of the silicon wafer, the oxide layer is arranged on the surface of the silicon wafer, so that the metal transited to the surface of the silicon wafer in the heat preservation stage is enriched in the interface state formed by the oxide layer, the metal content of the surface, subsurface and in-body of the silicon wafer can be truly tested, and particularly the content of metals such as copper, zinc and the like with high mobility is tested, so that the production process is effectively guided and controlled.
The method for testing the metal recovery rate of the silicon wafer surface is very practical in the manufacture of high-level silicon wafer products, and can be applied to the surface metal test of any silicon material in commerce.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, and it will be obvious to a person skilled in the art that other drawings can be obtained from these drawings without inventive effort.
FIG. 1 is a flow chart for testing the recovery rate of metal on the surface of a silicon wafer in the prior art;
FIG. 2 is a flow chart of a test of recovery rate of metal on the surface of a silicon wafer in an embodiment of the invention;
FIG. 3 is a schematic diagram of a system for testing recovery of metal from a silicon wafer surface in an embodiment of the invention.
Detailed Description
In order that the above objects, features and advantages of the invention will be more clearly understood, a further description of the invention will be made. It should be noted that, without conflict, the embodiments of the present invention and features in the embodiments may be combined with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced otherwise than as described herein; it will be apparent that the embodiments in the specification are only some, but not all, embodiments of the invention.
The currently adopted silicon wafer surface metal test flow is shown in figure 1. Because metal in the silicon wafer can jump to the surface of the silicon wafer in the storage process, the phenomenon that the recovery rate of the surface metal is qualified when the silicon wafer leaves a factory, but the surface metal becomes unqualified after storage possibly occurs, so that the test result cannot truly reflect the metal contamination level of the silicon wafer. The embodiment of the invention provides a method for testing the metal recovery rate of the surface of a silicon wafer, which is used for truly showing the metal contents of the surface, subsurface and in-vivo of the silicon wafer, so that the difficult problem that the measurement difference of the metal recovery rate of the surface is large when the silicon wafer leaves a factory and after storage and the quality of the silicon wafer cannot be accurately controlled is solved. The technical thought of the method for testing the metal recovery rate of the silicon wafer surface in the embodiment of the invention is as follows: wet oxidation of the silicon wafer to be tested in the high-temperature annealing module is carried out, and an oxide layer is formed on the surface of the silicon wafer to be tested; cooling to a certain temperature after oxidation, and preserving heat to enable in-vivo metal to diffuse into an oxidation layer; transmitting the silicon wafer to be tested to a hydrofluoric acid atomization corrosion module, and removing an oxide layer on the surface; liquid drops with a certain chemical liquid proportion are adopted to move on the surface of the silicon wafer according to a certain path, and surface metal is collected; metal level detection was performed using an inductively coupled plasma mass spectrometer.
Specifically, the method for testing the metal recovery rate of the surface of the silicon wafer according to the embodiment of the invention comprises the following steps, and a flow chart of the method is shown in fig. 2:
s1, placing a silicon wafer to be tested in an environment of 800-1200 ℃, introducing oxygen containing water vapor for oxidation, and forming an oxide layer on the surface of the silicon wafer to be tested;
s2, cooling to 150-600 ℃ and preserving heat;
s3, carrying out atomization corrosion on the silicon wafer to be tested, and removing an oxide layer;
s4, dropwise adding the corrosion liquid on the silicon wafer to be tested which is horizontally placed, and collecting the corrosion liquid after corroding the silicon wafer to be tested to obtain a sample liquid; repeating 3-n times, wherein n is more than or equal to 3 and less than or equal to 10, and obtaining at least 3 sample liquids;
s5, detecting the concentrations C1, C2, … … and Cn of different metals in each sample liquid, and calculating different metal recovery rates through the following formula:
metal recovery = C1/(c1+c2+ … … +cn) ×100%.
Wherein the metal on the surface of the silicon wafer is one or more selected from Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
According to the method for testing the metal recovery rate of the silicon wafer surface, the oxide layer is arranged on the silicon wafer surface, so that the metal which is transited to the silicon wafer surface in the heat preservation stage is enriched in the interface state formed by the oxide layer, and because the transition route of the metal is random, if the interface state formed by the oxide layer is not used for fixing and enriching the metal, the metal which is transited to the silicon wafer surface can be transited back into the silicon wafer again, and the metal cannot be effectively ensured to be fixed on the silicon wafer surface. The embodiment of the invention is researched, and the method of soaking and oxidizing by adopting the acidic hydrogen peroxide solution can possibly introduce metal ions in the acidic hydrogen peroxide solution, so that the content of the metal cannot be determined.
In the embodiment of the invention, the oxidation temperature is 800-1200 ℃, and under the condition of containing water molecules, an oxidation layer can be rapidly formed on the surface of the silicon wafer. If the temperature of oxidation is too low, the oxide film growth rate is slow, resulting in a decrease in the oxide film formation efficiency. The oxidation temperature is high and the oxidation efficiency is high, but the single crystal melting point is 1410 ℃, so that the oxidation temperature is not more than 1200 ℃, further preferably the oxidation temperature is not more than 1150 ℃, and preferably 1000 ℃ to 1100 ℃. The temperature for heat preservation is 150-600 ℃, preferably 200-300 ℃, and particularly can be 250 ℃; the heat preservation can adopt the residual temperature after high-temperature oxidation to ensure that the metal in the silicon chip transits to the surface of the silicon chip. If the temperature of the heat preservation is too low, the metal in the silicon wafer cannot be effectively transited out; if the temperature of the heat preservation is too high, the mobility of the metal increases and the metal returns to the inside of the silicon wafer.
As a preferable technical scheme of the embodiment of the invention, in the step S1, the oxidation time is 30 minutes to 3 hours, more preferably 1 to 2.5 hours, and still more preferably 2 hours. In the time, an oxide film with moderate thickness can be formed, so that the fixation and enrichment of metal can be satisfied, the corrosion in the step of atomization corrosion is easy, and meanwhile, the surface of the silicon wafer cannot be damaged.
As a preferable technical scheme of the embodiment of the invention, in S1, the flow rate of the oxygen containing water vapor is 0.1 mL/min-20L/min, more preferably 5 mL/min-20L/min, and still more preferably 10 mL/min-20L/min. Specifically, the formation of the oxide film can be adjusted. The content of water vapor in the oxygen is not particularly limited, and can meet the oxidation requirement within 2-5 v/v%.
As a preferable technical scheme of the embodiment of the invention, in S2, the cooling process becomes annealing, and the cooling rate is not particularly required. Nitrogen, helium or air can be introduced in the heat preservation process; in the annealing process, inert gases such as argon, nitrogen and the like can be adopted, and the annealing can also be performed in air; since a stable oxide film has been formed, there is no severe requirement for the atmosphere environment during the heat preservation.
As a preferable technical scheme of the embodiment of the invention, in the step S2, the heat preservation time is 30 minutes to 2 hours. During this time, efficient transition and enrichment of the metal can be accomplished. If the heat preservation time is further prolonged, the enrichment of metals has no further growing trend. If the time is too short, metal transitions and enrichment may have a tendency to be inadequate.
As a preferable technical scheme of the embodiment of the invention, in the step S3, the atomization corrosion by adopting the hydrofluoric acid solution can be performed by adopting a conventional method, and the concentration of the hydrofluoric acid solution is preferably 1% -50% by mass. The time of atomization corrosion is generally 15-20 min.
As a preferable technical solution of the embodiment of the present invention, in S4, the etching solution is hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70. The sampling on the surface of the silicon wafer can be carried out in a conventional mode, the surface of the silicon wafer is scanned in a moving way, the whole surface of the silicon wafer can be sampled, and the silicon wafer can be locally sampled, such as a ring shape, a fan shape, a semicircle shape and the like. And collecting the etching solution after etching the silicon wafer to be tested to obtain a sample solution.
As a preferred embodiment of the present invention, in S5, the detection may use an inductively coupled plasma mass spectrometer, for example, series devices such as ICP-MS 7800 manufactured by agilent corporation.
The second aspect of the embodiment of the invention also relates to a system for testing the metal recovery rate of the surface of the silicon wafer, which is applied to the method for testing the metal recovery rate of the surface of the silicon wafer in the first aspect, and comprises a high-temperature annealing module, an atomization corrosion module, a sampling module and a detection statistics module;
the high-temperature annealing module is used for oxidizing the silicon wafer to be tested at high temperature, cooling and preserving heat;
the atomization corrosion module is used for performing atomization corrosion on the silicon wafer to be tested;
the sampling module is used for dripping the corrosion liquid on the silicon wafer to be tested to obtain a sample liquid;
the detection statistical module is used for detecting the content of different metals in each sample liquid and calculating the recovery rate of the different metals. A schematic of the test system is shown in fig. 3.
The specific test method of the test system comprises the following steps:
s1, oxidizing a silicon wafer to be tested by wet oxygen in a high-temperature annealing module, and forming an oxide layer on the surface of the silicon wafer to be tested; cooling to a certain temperature after oxidation, and preserving heat to enable in-vivo metal to diffuse into an oxidation layer;
s3, transmitting the silicon wafer to be tested to an atomization corrosion module, and removing an oxide layer on the surface by adopting hydrofluoric acid;
s4, transmitting the silicon wafer to be tested to a sampling module, and moving liquid drops of the corrosive liquid on the surface of the silicon wafer according to a certain path to obtain a sample liquid;
and S5, detecting and calculating the metal level by using a detection statistics module to obtain the recovery rate of the metal on the surface of the silicon wafer.
As a preferable technical scheme of the embodiment of the invention, the high-temperature annealing module is used for oxidizing the silicon wafer to be tested at a high temperature, cooling and preserving heat, oxidizing the silicon wafer to be tested at the high temperature into oxygen containing water vapor, forming an oxide layer on the surface of the silicon wafer to be tested, and setting the oxidizing temperature to be any value of 800-1200 ℃. In the heat preservation process, metal is subjected to transition and enrichment in the interface state of an oxide layer, and the heat preservation temperature is set to be any value of 150-600 ℃.
The silicon wafer surface metal recovery rate test system provided by the embodiment of the invention can be used for effectively and truly testing the metal contents of the surface, subsurface and body of the silicon wafer, especially the metal contents of copper, zinc and the like, and effectively controlling the product quality.
The technical scheme and effect of the present invention will be further explained and illustrated by examples and comparative examples, which are commercially available as raw materials and instruments.
Example 1
P (100) produced by using a Czochralski method, wherein the same batch of 12-inch silicon polished 30 wafers with resistivity of 1-100 omega cm and thickness of 775 mu m are used as silicon wafers to be tested after polishing and cleaning procedures, 2 wafers are extracted, and the following method is adopted for testing, wherein the flow chart is shown in figure 2:
1. placing the silicon wafer to be tested in an environment of 1100 ℃ and introducing oxygen containing water vapor for oxidation for 2 hours, wherein the flow rate of the oxygen containing water vapor is 20L/min; forming an oxide layer on the surface of the silicon wafer to be tested;
2. cooling to 250 ℃ and preserving heat for 1.5 hours;
3. carrying out atomization corrosion on the silicon wafer to be tested for 15min, wherein the mass percentage concentration of hydrofluoric acid solution adopted in the atomization corrosion is 49%;
4. dropwise adding corrosion liquid on a silicon wafer to be tested which is horizontally placed, wherein the corrosion liquid is specifically hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70, moving and scanning the surface of the silicon wafer according to a certain path, and collecting etching liquid after etching the silicon wafer to be tested to obtain sample liquid; repeating for 3 times to obtain 3 sample solutions;
5. the concentration of different metals C1, C2, C3 in each sample fluid was measured by ICP-MS 7900 and the different metal recovery was calculated by the following formula:
metal recovery = C1/(c1+c2+c3) ×100%.
Wherein the silicon wafer surface metal comprises Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
The test results are shown in Table 1.
TABLE 1
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from Table 1, the metal concentration on the surface of the silicon wafer is higher and the recovery rate is higher after the test by the test method of the embodiment of the invention, and the metal contamination level of the silicon wafer can be effectively reflected.
2 pieces of the silicon wafer samples were taken out from the batch, and left for 6 months at a temperature of 22.+ -. 1 ℃ and a humidity of 40%.+ -. 5%, and the surface metal recovery rate was measured by the same method as in this example, to obtain test results as shown in Table 2:
TABLE 2
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from Table 2, after the test by the test method of the present invention, the metal concentration C1 and the recovery rate of the silicon wafer surface after a period of time are similar to those before the placement, and there is no significant difference, which indicates that the method of the present invention can accurately reflect the metal contamination level of the silicon wafer.
Example 2
P (100) produced by using a Czochralski method has a resistivity of 1-100 Ω cm and a thickness of 775 mu m, and is prepared by polishing 30 pieces of 12-inch silicon in the same batch, taking out 2 pieces of silicon wafers to be tested after polishing and cleaning, and testing by adopting the following method:
1. placing the silicon wafer to be tested in an environment of 800 ℃ and introducing oxygen containing water vapor for oxidation for 3 hours, wherein the flow rate of the oxygen containing water vapor is 10L/min; forming an oxide layer on the surface of the silicon wafer to be tested;
2. cooling to 600 ℃ and preserving heat for 0.5 hour;
3. carrying out atomization corrosion on the silicon wafer to be tested for 15min, wherein the mass percentage concentration of hydrofluoric acid solution adopted in the atomization corrosion is 50%;
4. dropwise adding corrosion liquid on a silicon wafer to be tested which is horizontally placed, wherein the corrosion liquid is specifically hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70, moving and scanning the surface of the silicon wafer according to a certain path, and collecting etching liquid after etching the silicon wafer to be tested to obtain sample liquid; repeating for 3 times to obtain 3 sample solutions;
5. the concentration of different metals C1, C2, C3 in each sample fluid was measured by ICP-MS 7900 and the different metal recovery was calculated by the following formula:
metal recovery = C1/(c1+c2+c3) ×100%.
Wherein the silicon wafer surface metal comprises Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
The test results are shown in Table 3.
TABLE 3 Table 3
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from Table 3, the metal concentration on the surface of the silicon wafer is higher and the recovery rate is higher after the test by the test method of the embodiment of the invention, and the metal contamination level of the silicon wafer can be effectively reflected.
2 pieces of the silicon wafer samples were taken out from the batch, and left for 6 months at a temperature of 22.+ -. 1 ℃ and a humidity of 40%.+ -. 5%, and the surface metal recovery rate was measured by the same method as in this example, to obtain test results as shown in Table 4:
TABLE 4 Table 4
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from Table 4, after the test by the test method of the present invention, the metal concentration C1 and the recovery rate of the silicon wafer surface after a period of time are similar to those before the placement, and there is no significant difference, which indicates that the method of the present invention can accurately reflect the metal contamination level of the silicon wafer.
Example 3
P (100) produced by using a Czochralski method has a resistivity of 1-100 Ω cm and a thickness of 775 mu m, and is prepared by polishing 30 pieces of 12-inch silicon in the same batch, taking out 2 pieces of silicon wafers to be tested after polishing and cleaning, and testing by adopting the following method:
1. placing the silicon wafer to be tested in a 1200 ℃ environment, and introducing oxygen containing water vapor to oxidize for 0.5 hour, wherein the flow rate of the oxygen containing water vapor is 0.1L/min; forming an oxide layer on the surface of the silicon wafer to be tested;
2. cooling to 150 ℃ and preserving heat for 2 hours;
3. carrying out atomization corrosion on the silicon wafer to be tested for 20 min, wherein the mass percentage concentration of hydrofluoric acid solution adopted in the atomization corrosion is 1%;
4. dropwise adding corrosion liquid on a silicon wafer to be tested which is horizontally placed, wherein the corrosion liquid is specifically hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70, moving and scanning the surface of the silicon wafer according to a certain path, and collecting etching liquid after etching the silicon wafer to be tested to obtain sample liquid; repeating for 3 times to obtain 3 sample solutions;
5. the concentration of different metals C1, C2, C3 in each sample fluid was measured by ICP-MS 7900 and the different metal recovery was calculated by the following formula:
metal recovery = C1/(c1+c2+c3) ×100%.
Wherein the silicon wafer surface metal comprises Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
The test results are shown in Table 5.
TABLE 5
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from Table 5, the metal concentration on the surface of the silicon wafer is higher and the recovery rate is higher after the test by the test method of the embodiment of the invention, and the metal contamination level of the silicon wafer can be effectively reflected.
2 pieces of the silicon wafer samples were taken out from the batch, and left for 6 months at a temperature of 22.+ -. 1 ℃ and a humidity of 40%.+ -. 5%, and the surface metal recovery rate was measured by the same method as in this example, and the test results were shown in Table 6:
TABLE 6
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from Table 6, after the test by the test method of the present invention, the metal concentration C1 and the recovery rate of the silicon wafer surface after a period of time are similar to those before the placement, and there is no significant difference, which indicates that the method of the present invention can accurately reflect the metal contamination level of the silicon wafer.
Comparative example 1
Using the same batch of silicon wafer samples in example 1, 2 following methods were withdrawn to test metal recovery. The specific flow chart is shown in fig. 1:
1. carrying out atomization corrosion on a silicon wafer to be tested for 15 minutes, wherein the mass percentage concentration of hydrofluoric acid used in the atomization corrosion is 49%;
2. dropwise adding corrosion liquid on a silicon wafer to be tested which is horizontally placed, wherein the corrosion liquid is specifically hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70, moving and scanning the mixed solution on the surface of the silicon wafer according to a certain path, and collecting the corrosive liquid after corroding the silicon wafer to be tested to obtain a sample liquid; repeating for 3 times to obtain 3 sample solutions;
3. the concentration of different metals C1, C2, C3 in each sample fluid was measured by ICP-MS 7900 and the different metal recovery was calculated by the following formula:
metal recovery = C1/(c1+c2+c3) ×100%.
Wherein the silicon wafer surface metal comprises Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
The metal test was then performed with ICP-MS 7900 and repeated three times, and the surface metal recovery was calculated as shown in table 7.
TABLE 7
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from table 7, the surface metal recovery averaged to a level of 90.8% and the concentration of metal was lower, significantly lower than in example 1.
2 silicon wafers are extracted from the batch of silicon wafer samples, and the silicon wafer samples are placed for 6 months under the conditions of the temperature of 22+/-1 ℃ and the humidity of 40+/-5%, and the metal recovery rate is measured in the same way as the comparative example, so that test results are shown in Table 8:
TABLE 8
| Na | Mg | Al | K | Ca | Cr | Mn | Fe | Ni | Co | Cu | Zn | |
| C1 | 5.01 | 10.26 | 12.11 | 4.98 | 2.83 | 4.58 | 2.21 | 7.24 | 3.86 | 3.31 | 16.80 | 15.52 |
| C2 | 0.26 | 0.44 | 0.68 | 0.23 | 0.12 | 0.20 | 0.13 | 0.49 | 0.25 | 0.18 | 0.85 | 0.61 |
| C3 | 0.15 | 0.46 | 0.13 | 0.15 | 0.09 | 0.07 | 0.06 | 0.19 | 0.07 | 0.06 | 0.18 | 0.33 |
| Recovery of metals | 92.5% | 91.9% | 93.7% | 92.8% | 93.2% | 94.6% | 92.1% | 91.3% | 92.4% | 93.3% | 94.2% | 94.3% |
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from table 8, after the test by the test method of the present comparative example, the metal recovery rate of the surface of the silicon wafer after a period of time and the recovery rate of the surface metal (particularly copper Cu and zinc Zn with high mobility) of the silicon wafer after the placement have significantly changed, which indicates that the method cannot accurately reflect the metal contamination level of the silicon wafer.
Comparative example 2
Using the same lot of silicon wafers to be tested in example 1, 2 pieces were extracted for testing by the following method:
1. placing the silicon wafer to be tested at 250 ℃ and preserving heat for 2 hours;
2. carrying out atomization corrosion on the silicon wafer to be tested for 15min, wherein the mass percentage concentration of hydrofluoric acid adopted in the atomization corrosion is 49%;
3. dropwise adding corrosion liquid on a silicon wafer to be tested which is horizontally placed, wherein the corrosion liquid is specifically hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70, moving and scanning the mixed solution on the surface of the silicon wafer according to a certain path, and collecting the corrosive liquid after corroding the silicon wafer to be tested to obtain a sample liquid; repeating for 3 times to obtain 3 sample solutions;
4. the concentration of different metals C1, C2, C3 in each sample fluid was measured by ICP-MS 7900 and the different metal recovery was calculated by the following formula:
metal recovery = C1/(c1+c2+c3) ×100%.
Wherein the silicon wafer surface metal comprises Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
The test results are shown in Table 9.
TABLE 9
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
It can be seen from table 9 that if the oxide layer is not prepared, the surface metal recovery rate averages to 93%, and the metal concentration C1 is at a lower level, as compared with table 1, it is known that effective fixation and enrichment of the transition metal cannot be achieved, resulting in a test result with a lower surface metal recovery rate.
Comparative example 3
Using the same lot of silicon wafers to be tested in example 1, 2 pieces were extracted for testing by the following method:
the detection method is different from example 1 in that in step 1, the high temperature environment is 700 ℃.
The test results are shown in Table 10.
Table 10
Wherein, the concentration units of C1, C2 and C3 are 10E8 atoms/cm 2 。
As can be seen from table 10, if an effective oxide layer cannot be prepared, the surface metal recovery rate averages to 93%, and the metal concentration C1 is at a lower level, as compared with table 1, effective fixing and enrichment of the transition metal cannot be achieved, resulting in a test result with a lower surface metal recovery rate.
The foregoing is only a specific embodiment of the invention to enable those skilled in the art to understand or practice the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown and described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. The method for testing the metal recovery rate of the surface of the silicon wafer is characterized by comprising the following steps of:
s1, placing a silicon wafer to be tested in an environment of 800-1200 ℃, introducing oxygen containing water vapor for oxidation, and forming an oxide layer on the surface of the silicon wafer to be tested;
s2, cooling to 150-600 ℃ and preserving heat;
s3, carrying out atomization corrosion on the silicon wafer to be tested, and removing the oxide layer;
s4, dropwise adding corrosion liquid on the silicon wafer to be tested which is horizontally placed, and collecting corrosion liquid after corroding the silicon wafer to be tested to obtain sample liquid; repeating 3-n times, wherein n is more than or equal to 3 and less than or equal to 10, and obtaining at least 3 sample liquids;
s5, detecting the concentrations C1, C2, … … and Cn of different metals in each sample liquid, and calculating different metal recovery rates through the following formula:
metal recovery = C1/(c1+c2+ … … +cn) ×100%.
2. The method of claim 1, wherein the silicon wafer surface metal is selected from one or more of Na, mg, al, K, ca, cr, mn, fe, ni, co, cu and Zn.
3. The test method according to claim 1, wherein in S1, the time of the oxidation is 30 minutes to 3 hours.
4. The test method according to claim 1, wherein in S1, the flow rate of the oxygen gas containing water vapor is 0.1 mL/min to 20L/min.
5. The test method according to claim 1, wherein in S2, nitrogen, helium or air is introduced into the incubation; the heat preservation time is 30 minutes to 2 hours.
6. The test method according to claim 1, wherein in S3, the atomized corrosion is performed by using a hydrofluoric acid solution, and the concentration of the hydrofluoric acid solution is 1% -50% by mass.
7. The test method according to claim 1, wherein in S4, the composition of the etching solution is hydrofluoric acid: hydrogen peroxide: the volume ratio of deionized water is 2:28:70.
8. the method of testing according to claim 1, wherein in S5, the detecting employs an inductively coupled plasma mass spectrometer.
9. A system for testing the metal recovery rate of the surface of a silicon wafer, which is characterized by applying the method for testing the metal recovery rate of the surface of the silicon wafer according to any one of claims 1-8, and comprising a high-temperature annealing module, an atomization corrosion module, a sampling module and a detection statistics module;
the high-temperature annealing module is used for oxidizing the silicon wafer to be tested at high temperature, cooling and preserving heat;
the atomization corrosion module is used for performing atomization corrosion on the silicon wafer to be tested;
the sampling module is used for dripping corrosion liquid on the silicon wafer to be tested to obtain sample liquid;
the detection statistical module is used for detecting the content of different metals in each sample liquid and calculating the recovery rate of the different metals.
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