WO2013084410A1 - シリコン単結晶の評価方法およびシリコン単結晶の製造方法 - Google Patents
シリコン単結晶の評価方法およびシリコン単結晶の製造方法 Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims abstract description 138
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 99
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 99
- 239000010703 silicon Substances 0.000 title claims abstract description 99
- 238000000034 method Methods 0.000 title claims abstract description 71
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 239000001301 oxygen Substances 0.000 claims abstract description 200
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 200
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 198
- 238000010438 heat treatment Methods 0.000 claims abstract description 77
- 238000009792 diffusion process Methods 0.000 claims abstract description 8
- 239000000969 carrier Substances 0.000 claims description 33
- 238000011156 evaluation Methods 0.000 claims description 18
- 125000004429 atom Chemical group 0.000 description 29
- 239000000523 sample Substances 0.000 description 19
- 238000002474 experimental method Methods 0.000 description 15
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- 235000012431 wafers Nutrition 0.000 description 9
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- 238000005204 segregation Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000002835 absorbance Methods 0.000 description 1
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- 229910002804 graphite Inorganic materials 0.000 description 1
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Classifications
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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
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/322—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to modify their internal properties, e.g. to produce internal imperfections
- H01L21/3221—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to modify their internal properties, e.g. to produce internal imperfections of silicon bodies, e.g. for gettering
- H01L21/3225—Thermally inducing defects using oxygen present in the silicon body for intrinsic gettering
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/02—Elements
- C30B29/06—Silicon
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
- C30B33/02—Heat treatment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions
Definitions
- the present invention relates to a method for evaluating a silicon single crystal and a method for producing a silicon single crystal, and in particular, silicon containing oxygen grown by a Czochralski method (CZ method), a magnetic field application CZ method (MCZ method), or the like.
- CZ method Czochralski method
- MZ method magnetic field application CZ method
- the present invention relates to a single crystal evaluation method and a manufacturing method.
- a wafer having a thin oxide film and a thin silicon layer formed on the surface layer of a silicon substrate called SOI (Silicon on Insulator) may be used. In this case, high resistivity is also desired.
- Patent Document 1 and Patent Document 2 propose a method in which oxygen atoms are diffused outward by high-temperature heat treatment to reduce the concentration in the vicinity of the surface of the substrate on which the device is formed.
- this method has a problem that the cost is increased because a high-temperature heat treatment step is required.
- Patent Document 3 discloses a technique for reducing oxygen and achieves a considerably low oxygen concentration.
- the top side (head side) of the crystal has a high oxygen concentration and is difficult to lower. Therefore, the lower the target oxygen concentration to be achieved, the lower the yield rate.
- Patent Document 4 discloses a method for obtaining an oxygen donor generation amount in advance in a high resistivity crystal. Although it is assumed here that the amount of oxygen donor generated is proportional to the oxygen concentration to the B power (see paragraph 40 of Patent Document 4), the specific numerical value is not finally disclosed. Further, FIG. 2 of Patent Document 4 shows that the oxygen concentration and the oxygen donor generation amount have a linear relationship on a semilogarithmic graph. If it is proportional to the Bth power of the oxygen concentration, there should be no linear relationship on the semilogarithmic graph. Therefore, the generated amount cannot be expressed as an equation from this method, and it is considered that there is no generality.
- [Oi] is the oxygen concentration in the silicon single crystal
- T is the temperature of the heat treatment
- t is the time of the heat treatment
- D (T) is the oxygen diffusion coefficient at the temperature T.
- the present invention has been made in view of the above-described problems, and provides a method that can evaluate the generation amount of carriers caused by oxygen donors more universally in a silicon single crystal. With the goal. It is another object of the present invention to provide a method for growing and manufacturing a silicon single crystal capable of achieving a desired resistivity even when oxygen donors are generated and the resistivity of the substrate is shifted.
- the heat treatment referred to here is a heat treatment near 450 ° C. at which oxygen donors are easily generated, and can be a heat treatment at a relatively low temperature of about 400 to 500 ° C.
- the oxygen concentration in the silicon single crystal to be evaluated can be 9 ⁇ 10 17 atoms / cm 3 (ASTM′79) or less.
- the amount of carriers generated due to oxygen donors can be calculated using the relational expression, and the resistivity of the silicon single crystal after the heat treatment can be calculated and evaluated using the calculated amount of carriers generated. .
- the present invention calculates the resistivity of the silicon single crystal after the heat treatment using the silicon single crystal evaluation method described above, and based on the calculated resistivity, the oxygen concentration when growing the silicon single crystal And a method for producing a silicon single crystal, characterized in that a target value of resistivity is determined and a silicon single crystal is grown based on the determined target value.
- the amount of carriers generated due to the oxygen donor generated by the heat treatment and the resulting shift in resistivity Since the silicon single crystal can be grown based on this, even if an oxygen donor is generated after the heat treatment and the resistivity is shifted, the resistivity after the shift can be set to a target value, and a desired product can be obtained. It becomes possible to obtain. And generation
- the silicon single crystal evaluation method of the present invention can be widely applied not only to a high oxygen concentration in a silicon single crystal but also to a low oxygen concentration, and more versatile. Therefore, it is possible to evaluate with higher accuracy than in the past. Furthermore, if the silicon single crystal manufacturing method of the present invention is used, it is possible to grow and manufacture a silicon single crystal in consideration of the amount of carriers generated due to oxygen donor due to heat treatment, and finally to a desired resistivity. Can be obtained.
- FIG. 1 is a flowchart showing an example of the procedure of this method.
- Step 1 Preparation of silicon single crystal to be evaluated A silicon single crystal to be evaluated is prepared. In this method, since the amount of carriers generated due to oxygen donors is determined, oxygen can be included in particular. For example, a silicon single crystal by CZ method or MCZ method can be prepared.
- the single crystal pulling apparatus 1 is arranged around a pulling chamber 2, a crucible 3 (quartz crucible on the inside, a graphite crucible on the outside) provided in the pulling chamber 2, and the crucible 3.
- a heater 4 a crucible holding shaft 5 for rotating the crucible 3 and its rotating mechanism (not shown), a seed chuck 7 for holding a silicon seed crystal 6, a wire 8 for pulling up the seed chuck 7, and a wire 8
- a winding mechanism (not shown) that rotates or winds is provided.
- a heat insulating material 9 is disposed around the outside of the heater 4.
- the silicon single crystal 10 is pulled up by a wire 8 from a raw material silicon melt 11.
- the seed held by the seed chuck 7 is retained in the silicon melt 11 in the crucible 3 while rotating the crucible 3.
- the crystal 6 is immersed.
- the rod-shaped silicon single crystal 10 is pulled up from the silicon melt 11 while rotating and winding the wire 8.
- the crucible 3 can be moved up and down in the direction of the crystal growth axis by the crucible holding shaft 5, and the crucible 3 is raised so as to compensate for the liquid level drop of the melt that has been crystallized and decreased during crystal growth.
- An inert gas is flowed to the side of the crystal in order to rectify the oxidizing vapor emitted from the silicon melt 11.
- the quartz crucible containing the silicon melt 11 is composed of silicon and oxygen, oxygen atoms are eluted into the silicon melt.
- the oxygen atoms move by convection in the silicon melt 11 and finally evaporate from the surface of the melt.
- most of the oxygen evaporates, but part of the oxygen is taken into the crystal and becomes interstitial oxygen Oi.
- the convection flow in the silicon melt 11 is changed by changing the rotational speed of the crucible 3 or the silicon single crystal 10 to be grown or by changing the magnetic field application condition in the magnetic field application CZ method (that is, the MCZ method). It is possible to control the oxygen concentration in the crystal, and it is possible to control the amount of oxygen evaporated from the surface by adjusting the flow rate of the inert gas and controlling the pressure in the furnace.
- the CZ method and the MCZ method can be selectively used according to the target value of the oxygen concentration.
- a silicon single crystal can be grown while adjusting the oxygen concentration. Then, a wafer-like sample is cut out of the obtained silicon single crystal with a band saw or the like.
- the oxygen concentration can be obtained by using this wafer-like sample, for example, by the FT-IR method at room temperature.
- the oxygen concentration [Oi] is described as Oi because the oxygen atom exists in the interstitial (interstitial) position in the silicon crystal, and the infrared absorption at that position is This is because it is measured and expressed as oxygen concentration.
- the oxygen concentration of the silicon single crystal to be evaluated is not particularly limited, and can be appropriately determined according to the purpose of evaluation. This technique is particularly useful for low oxygen crystals having an oxygen concentration of 9 ⁇ 10 17 atoms / cm 3 (ASTM'79) or less.
- the sample is subjected to an oxygen donor erasing heat treatment.
- An oxygen donor is present in the crystal after the silicon single crystal is grown.
- the oxygen donor is generated in a relatively low temperature region around 450 ° C.
- the bottom side of the crystal (the tail side: the part to be grown later) does not receive such a low-temperature thermal history during crystal growth and generates almost no oxygen donor.
- the top side of the crystal (head side: the portion grown earlier) is sufficiently subjected to this low-temperature thermal history, so that many oxygen donors are generated. With the recent increase in crystal length, this tendency becomes more prominent, and there is a large amount of oxygen donor on the top side and almost no oxygen donor on the bottom side.
- this oxygen donor is erased by a slight heat treatment at 650 ° C. for about 20 minutes, for example.
- Various other donor erasing heat treatments have been proposed.
- RTA Rapid Thermal Anneal
- the temperature and time are not particularly specified, and are due to oxygen. Since any method can be used as long as the generated thermal donor can be erased, the heat treatment is performed at 650 ° C. for 20 minutes.
- the PN determination is performed, and then the resistivity is measured using, for example, a four-probe method.
- the method for measuring the resistivity is not particularly limited, and an appropriate method can be selected.
- the carrier concentration is obtained from the measured resistivity by using an Irvin curve. As described above, a sample of a silicon single crystal to be evaluated is prepared, and the oxygen concentration, carrier concentration, resistivity, and the like are examined in advance.
- Step 2 Calculation of Oxygen Donor-Derived Carrier Generation Using Relational Expression and Evaluation of Silicon Single Crystal
- ⁇ [C] ⁇ [Oi] 5 ⁇ exp ( ⁇ ⁇ D (T) [Oi] ⁇ t) (where ⁇ and ⁇ are constants), the amount of carriers generated due to oxygen donors is calculated.
- [Oi] is the oxygen concentration in the silicon single crystal
- T is the temperature of the heat treatment
- t is the time of the heat treatment
- D (T) is the oxygen diffusion coefficient at the temperature T.
- the oxygen concentration [Oi] in the silicon single crystal in the above relational expression is the oxygen concentration obtained in step 1 by the FT-IR method or the like.
- the temperature T of heat processing can be suitably determined according to the objective etc. For example, if the amount of carriers generated due to an oxygen donor due to heat treatment performed in a process such as wiring or package after the device process is obtained, it can be set to the same value as that actually performed in that process. . Any heat treatment condition may be used as long as an oxygen donor is generated.
- the heat treatment temperature can be about 400 to 500 ° C.
- the heat treatment time t can be appropriately determined in the same manner.
- the constants ⁇ and ⁇ are constants determined by each measurement condition.
- the oxygen concentration is measured by FT-IR, and the oxygen concentration is converted from the absorbance obtained by subtracting the reference from the absorption peak.
- the conversion coefficient varies depending on the reference, varies depending on the measuring instrument, and also varies depending on the measuring instrument manufacturer. Therefore, even if the same sample is measured, it depends on which conversion factor is used.
- Some measuring device manufacturers display the oxygen concentration in ppma, and some measuring device manufacturers display in atoms / cm 3 .
- Oxygen concentration [Oi] 9.2 ⁇ 10 17 , 10.8 ⁇ 10 17 , 12.8 ⁇ 10 17 , 13.8 ⁇ 10 17 , 15.9 ⁇ 10 17 atoms / cm 3 (ASTM'79) A sample was prepared.
- each sample was subjected to a donor killer heat treatment, PN determination and resistivity measurement were performed, and then a heat treatment at 450 ° C. at which oxygen donors are easily generated to generate oxygen donors for 1 hour (3600 seconds) and 15 hours (54000 seconds). 2).
- This sample was again subjected to PN determination and resistivity measurement.
- the carrier concentration was determined from the Irvine curve. Since a P-type sample was used this time, the amount of carriers generated due to oxygen donors was obtained by subtracting the carrier concentration after heat treatment from the carrier concentration before heat treatment. However, in the sample inverted to the N type after the heat treatment, the sum of the carrier concentration before the heat treatment and the carrier concentration after the heat treatment was defined as the oxygen donor-derived carrier generation amount.
- FIG. 9 plots these carrier generation amounts ⁇ [C] against oxygen concentration [Oi].
- Equation (1) obtained in this way is shown on the FIG. 9 with a broken line at 450 ° C. for 1 hour and a solid line at 450 ° C. for 15 hours. As a result, it agrees well with the experimental value, and it seems that Equation (1) is correct.
- Example 2 Next, it was confirmed whether Formula (1) can be used by expanding the range to a lower oxygen concentration region. Similar to Experiment 1, a sample with varying oxygen concentration was prepared. However, the level of oxygen is lower than in Experiment 1, and is 4.8 ⁇ 10 17 , 5.2 ⁇ 10 17 , 5.8 ⁇ 10 17 , 6.8 ⁇ 10 17 , 8.0 ⁇ 10 17 atoms / cm 3. (ASTM '79). Since it was necessary to lower the oxygen concentration, all samples of this time were produced using the MCZ method with a magnetic field applied.
- the oxygen concentration is 9 ⁇ 10 17 atoms / cm 3 (ASTM'79), and the experimental value and equation (1) agree well in the higher oxygen concentration region than that, but in the case where the oxygen concentration is lower, I understand that I have not done it.
- This discrepancy is due to the fact that none of the references referred to are relatively old, and the MCZ method has not become so widespread, and it is not necessary to lower the oxygen concentration that is a characteristic of CZ crystals and has the effect of gettering. This is probably because there were few samples with such a low oxygen concentration.
- thermal donors act as nuclei for oxygen precipitation. In this high oxygen region, growth from thermal donors to oxygen precipitates is considered to have prevented accurate description. In any case, as long as the conventional oxygen concentration is handled, it is considered that there is no inconvenience in the equation (1).
- ⁇ [C] 4.53 ⁇ 10 ⁇ 39 ⁇ [Oi] 3 ⁇ exp in the experimental result (point) on the low oxygen concentration side in FIG. ( ⁇ 1.63 ⁇ 10 ⁇ 5 ⁇ D (T) ⁇ [Oi] ⁇ t) (line) does not match.
- the experimental value is smaller than that of the equation (1). Therefore, the influence of the oxygen concentration given by the equation (1) (proportional to [Oi] 3 ) is weak, and it is estimated that the influence of the oxygen concentration is actually larger. Therefore, when fitting was performed assuming that the oxygen concentration [Oi] was proportional to the fourth, fifth, and sixth powers, the best match was found when it was assumed that the oxygen concentration was proportional to the fifth power.
- Equation (2) The coefficients ⁇ and ⁇ obtained at that time are expressed by Equation (2).
- a major feature of the equation (2) is that a portion that has been conventionally proportional to the third power of the oxygen concentration [Oi] is proportional to the fifth power. This indicates that a donor is formed with 3 to 4 oxygen atoms in the past, but actually shows that a little more oxygen is involved and an oxygen donor is formed. This is a point clarified by the evaluation of the low oxygen concentration region than before.
- FIG. 3 is a graph describing both the expression (2) and the results of Experiment 1 and Experiment 2. The experimental results can be expressed well over the entire oxygen concentration. From the above, it is considered appropriate to obtain the generation amount of oxygen donor-derived carriers by the equation (2).
- the relational expression in the present invention was derived as described above.
- the amount of carriers generated due to oxygen donors in the silicon single crystal can be calculated and obtained, and the silicon single crystal can be evaluated. Furthermore, since the carrier generation amount can be obtained, the resistivity after the heat treatment can be estimated from the addition or subtraction of the carrier concentration calculated from the resistivity of the corresponding silicon single crystal.
- the addition or subtraction is described because it depends on the conductivity type of the original silicon single crystal. This is because if the original crystal is N-type, addition is performed, and if it is P-type, subtraction is performed. Further, when the amount of oxygen donor-derived carriers generated is larger than the P-type carrier concentration, it is called N-transfer and changes to N-type.
- the P-type carrier concentration is subtracted from the oxygen donor-derived carrier concentration. Can be calculated as the N-type carrier concentration.
- the relationship between the carrier concentration and the resistivity can be calculated using an Irvine curve. In this way, the resistivity can be calculated and evaluated for the silicon single crystal after the heat treatment.
- the evaluation method of the present invention unlike the conventional case, not only when the oxygen concentration in the silicon single crystal is high, but also low concentration (for example, 9 ⁇ 10 17 atoms / cm 3 (ASTM ′ 79) or less), the amount of carriers generated due to oxygen donors, the resistivity after heat treatment, and the like can be appropriately evaluated. This is a more versatile evaluation method than in the past.
- the evaluation method of the present invention as shown in FIG. 1 is performed. And, as mentioned above, the expected resistivity after low-temperature heat treatment can be calculated. Based on this, the oxygen concentration and resistivity of the silicon wafer to be input to the corresponding process including the low-temperature heat treatment are determined. Is possible.
- the CZ method a crystal is generally grown after introducing a dopant for controlling resistance into the crucible. At this time, the resistivity of the dopant changes on the top side and the bottom side of the crystal due to a segregation phenomenon. When shipping to the customer, the part that satisfies the requirement is shipped. Therefore, if the required resistivity range is narrow, the product length is shortened.
- a high resistivity crystal of about 50 ⁇ cm or more as described above, carriers due to oxygen donors are generated by low-temperature heat treatment performed in the final step of wiring and package, and the resistivity at the time when the crystal is grown is It can be different. Therefore, if this method is used, the oxygen concentration dependence of the oxygen donor-derived carriers to be generated is easily obtained from the low temperature heat treatment temperature and time applied in the final step of the wiring or package. Therefore, the optimum resistivity and oxygen concentration can be freely designed.
- the oxygen concentration is aimed at A 1 atoms / cm 3 (ASTM'79)
- the amount of carriers generated is B 1 atoms / cm 3
- the target resistivity is C 1 ⁇ cm accordingly.
- the product part is shortened accordingly.
- the crystal is grown with the aim of oxygen concentration A 2 atoms / cm 3 (ASTM'79) on the top side of the crystal, so that the resistivity target is C 2 ⁇ cm, and the oxygen concentration is A 2 'on the crystal bottom side. Since it is lowered to atoms / cm 3 (ASTM '79), the design of extending the product length to D 2 cm becomes possible.
- target values such as oxygen concentration and resistivity when growing silicon single crystals and the target values so that the desired quality can be obtained after low-temperature heat treatment.
- the silicon single crystal is grown using the single crystal pulling apparatus 1 as shown in FIG. 2 based on the determined conditions (crucible rotation speed, dopant amount, etc.). That's fine. Then, it is possible to obtain a desired silicon wafer through an originally scheduled process.
- the resistance is changed by a small amount of oxygen donor-derived carriers.
- the resistance is not limited to this.
- this method can be applied in any resistivity range and is desirable.
- Example 1 In addition to the sample used in Experiment 2, a low oxygen concentration sample having an oxygen concentration of 2.9 to 8.9 ⁇ 10 17 atoms / cm 3 (ASTM'79) was prepared. Not only P type but also N type sample is included. These samples were evaluated by calculating the amount of carriers generated from oxygen donors using the relational expression in the present invention (in this case, expression (2)). Evaluation was performed not only when the heat treatment time at 450 ° C. was 1 hour and 15 hours, but also when the heat treatment time was 5 hours and 10 hours. A graph obtained by the relational expression is shown in FIG. 4 for each heat treatment time.
- the graph of the carrier generation amount obtained as described above was confirmed by actually performing the heat treatment.
- the amount generated was obtained by subtracting the carrier concentration obtained from the resistivity before heat treatment from the carrier concentration obtained from the resistivity after heat treatment.
- Equation (2) can express the experimental result well. It can also be seen that this formula can be used without any problem for either P-type or N-type.
- Example 2 A P-type wafer having a resistivity of 1000 ⁇ cm to 2000 ⁇ cm was required.
- the low-temperature heat treatment performed in the final stage of the device is a process corresponding to 2 hours at 450 ° C. Therefore, we studied to achieve this goal.
- Crystals were manufactured by the MCZ method, and the crystals were grown using an apparatus having a crucible size of 26 inches (66 cm).
- the oxygen concentration on the top side of the crystal is difficult to decrease.
- the apparatus of FIG. 2 is used and the oxygen concentration [Oi] is aimed at 4 ⁇ 10 17 atoms / cm 3 (ASTM'79) and 8 ⁇ 10 17 atoms / cm 3 (ASTM'79).
- Equation (2) the amount of carriers generated due to oxygen donors generated by heat treatment at 450 ° C. for 2 hours is calculated and shown in FIG. As shown in FIG. 5, the cases where the oxygen concentration [Oi] is 4 ⁇ 10 17 , 5 ⁇ 10 17 , 6 ⁇ 10 17 , 7 ⁇ 10 17 atoms / cm 3 (ASTM'79) were estimated.
- the calculated oxygen concentration [Oi] is 4 ⁇ 10 17 , 5 ⁇ 10 17 , 6 ⁇ 10 17 , 7 ⁇ 10 17 atoms / cm 3 (ASTM'79) and the oxygen concentration [Oi] is 0 atoms / cm 3 ( Based on the carrier generation amount in the case of ASTM '79), the resistivity distribution in the crystal length direction when oxygen donor-derived carriers are generated after the low-temperature heat treatment is plotted in FIG. 6 for each oxygen concentration. did.
- the target resistivity on the crystal top side was set to 1900 ⁇ cm.
- the resistivity of the crystal is high on the top side and low on the bottom side due to the segregation phenomenon of the dopant. Therefore, the resistivity on the top side is aimed at a value close to the higher one of the standard 1000 to 2000 ⁇ cm.
- the aim was set here so that the resistivity on the top side would be 1900 ⁇ cm.
- Example 3 As in Example 2, the low-temperature heat treatment performed at the final stage of the device was equivalent to 2 hours at 450 ° C., and a P-type wafer having a resistivity of 1000 ⁇ cm to 2000 ⁇ cm was required.
- the oxygen concentration [Oi] is 4 ⁇ 10 17 atoms / cm 3 (ASTM ′) when growing a silicon single crystal. 79) was suggested.
- the resistivity is obtained when the oxygen concentration [Oi] in FIG. 6 is 4 ⁇ 10 17 atoms / cm 3 (ASTM'79). Can be obtained.
- the resistivity to be aimed at is determined from the oxygen concentration when the crystal is grown under the condition that the oxygen concentration can be lowered without difficulty, and a design that can take as much product as possible is performed. .
- an oxygen concentration profile as shown in FIG. 7 is obtained.
- the resistivity on the bottom side was determined as the standard.
- the target resistivity on the top side was designed so that the lower limit value was 1000 ⁇ or more and 1050 ⁇ cm in consideration of the target error. The result is shown by a solid line in FIG. As a result of the above consideration, the resistivity to be aimed at was about 1350 ⁇ cm on the top side. Further, in consideration of the carrier generation amount calculated from the above oxygen concentration, the resistivity expected after the device process is also shown by a broken line in FIG.
- the solidification rate was about 0.11, and the resistivity after the device was within the standard, so that a design effective for the solidification rate of 0.11 to 0.7 as a product was completed.
- a silicon single crystal was grown based on this design.
- a wafer-like sample was cut out from the grown crystal, subjected to donor killer heat treatment, and the resistivity was measured. As a result, a resistivity corresponding to the solid line in FIG. 8 was obtained.
- Example 3 In response to the same requirements as in Example 3, crystals were grown without using this method. Since the resistivity standard is 1000 ⁇ cm to 2000 ⁇ cm without considering the amount of carriers generated due to oxygen donors, the resistivity was set to 1900 ⁇ cm on the top side of the crystal. The resistivity calculated from this aim is shown by a one-dot chain line in FIG. The oxygen concentration was the same profile as in Example 3.
- the resistivity profile showed a distribution equivalent to the dotted line in FIG. 8 of the resistivity profile expected after the device heat treatment obtained from Equation (2).
- the length of the product that satisfies the standard after the device process becomes a solidification rate of 0.25 to 0.7. The product length has been reduced compared to 0.11 to 0.7.
- the present invention is not limited to the above embodiment.
- the above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.
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Abstract
Description
しかし近年CMOSプロセスの微細化が進んだこと、低コスト化したいことなどから、シリコンをベースとしたRFデバイスが実現可能となってきた。
しかしこの方法では、高温の熱処理工程が必要なために高コスト化してしまうという問題点がある。
また、特許文献4の図2では酸素濃度と酸素ドナー発生量とが片対数グラフ上で直線の関係になることが示されている。酸素濃度のB乗に比例するのであれば片対数グラフ上で直線関係になるはずはないので、結局この方法からは数式として発生量を表記できておらず、汎用性がないと考えられる。
ここで、酸素ドナー等については、国際公開第2005/071144号や、非特許文献のW. Kaiser et al., Phys. Rev. 112, 1546 (1958)、また、K.wada et al., in Semiconductor Silicon/1986 edited by H.R.Huff et al. (Electrochemical Society, Pennington NJ, 1986),p.778、さらにはH.Takeno et al., J. Appl. Phys. 84, 3117 (1998)などに記載されており、本発明者らは、それらの記載に基づき、酸素ドナーに起因して発生するキャリア濃度を数値化することを試みた。
Δ[C]=α’[Oi]3×exp(-β’・D(T)・[Oi]・t) (ここでα’、β’は定数)、と表されることである。なお、[Oi]はシリコン単結晶中の酸素濃度、Tが熱処理の温度、tが前記熱処理の時間、D(T)が温度Tでの酸素拡散係数である。
また、酸素ドナーが生成されて基板の抵抗率がシフトしても、所望の抵抗率とすることが可能なシリコン単結晶を育成して製造する方法を提供することを目的とする。
なお、ここでいう熱処理は酸素ドナーが生成されやすい450℃近辺の熱処理であり、例えば400-500℃程度の比較的低温の熱処理とすることができる。
さらには、本発明のシリコン単結晶の製造方法であれば、熱処理による酸素ドナー起因のキャリアの発生量を考慮してシリコン単結晶を育成して製造することができ、最終的に所望の抵抗率を有する製品を得ることができる。
まず、本発明のシリコン単結晶の評価方法について説明する。
図1は本方法の手順の一例を示すフロー図である。
(工程1) 評価対象のシリコン単結晶の用意
評価対象となるシリコン単結晶を用意する。
本方法では、酸素ドナーを起因とするキャリアの発生量について求めるので、特には酸素を含むものとすることができる。例えば、CZ法やMCZ法によるシリコン単結晶を用意することができる。
ここで、CZ法等によりシリコン単結晶を育成可能な装置について図2を用いて説明する。
図2に示すように、単結晶引上げ装置1は、引上げ室2と、引上げ室2中に設けられたルツボ3(内側に石英ルツボ、外側に黒鉛ルツボ)と、ルツボ3の周囲に配置されたヒータ4と、ルツボ3を回転させるルツボ保持軸5及びその回転機構(図示せず)と、シリコンの種結晶6を保持するシードチャック7と、シードチャック7を引上げるワイヤ8と、ワイヤ8を回転又は巻き取る巻取機構(図示せず)を備えて構成されている。また、ヒータ4の外側周囲には断熱材9が配置されている。
シリコン単結晶10は、原料のシリコン融液11からワイヤ8によって引上げられる。
ルツボ3はルツボ保持軸5により結晶成長軸方向に昇降可能であり、結晶成長中に結晶化して減少した融液の液面下降分を補うように該ルツボ3を上昇させる。結晶の側方にはシリコン融液11から発する酸化性蒸気を整流するために不活性ガスが流されている。
このときにルツボ3や育成するシリコン単結晶10の回転数を変更したり、磁場印加CZ法(すなわちMCZ法)では磁場印加条件を変更したりすることでシリコン融液11内の対流の流れを制御して結晶中の酸素濃度を制御することが可能であるし、また不活性ガスの流量調整や炉内の圧力制御により表面からの酸素蒸発量を制御可能である。
なお、酸素濃度はこのウェーハ状のサンプルを用いて、例えば、室温でのFT-IR法によって求めることができる。ここで酸素濃度[Oi]でOiと記載しているのは、酸素原子がシリコン結晶中ではインタースティシャル(格子間)の位置に存在しているためであり、その位置での赤外吸収を測定して酸素濃度と表記しているためである。
なお、本手法は酸素濃度9×1017atoms/cm3(ASTM’79)以下の低酸素の結晶に対して特に有用である。
シリコン単結晶育成後の結晶中には酸素ドナーが存在している。酸素ドナーは450℃前後の比較的低温領域で生成される。結晶のボトム側(尾側:後に育成される部分)では結晶成長時にこのような低温熱履歴を受けず、ほとんど酸素ドナーが発生しない。逆に結晶のトップ側(頭側:先に育成される部分)では充分にこの低温熱履歴を受けるため、多くの酸素ドナーが生成される。
近年の結晶長尺化に伴い、この傾向は一層顕著となり、トップ側では大量の酸素ドナーが存在し、ボトム側には酸素ドナーがほとんど存在しない、という状況となっている。
そして、該測定した抵抗率からアービンカーブを用いてキャリア濃度を求める。
以上のようにして、評価対象のシリコン単結晶のサンプルを用意し、酸素濃度やキャリア濃度、抵抗率等を予め調べておく。
次に、関係式:Δ[C]=α[Oi]5×exp(-β・D(T)・[Oi]・t) (ここでα、βは定数)を用いて、酸素ドナーを起因とするキャリアの発生量を算出する。
上記関係式において、[Oi]はシリコン単結晶中の酸素濃度であり、Tが熱処理の温度、tが前記熱処理の時間、D(T)が温度Tでの酸素拡散係数である。
また、熱処理の温度Tは、目的等に応じて適宜決定することができる。例えば、デバイス工程後の配線やパッケージなどの工程で行われる熱処理による酸素ドナーを起因とするキャリアの発生量を求めるのであれば、実際にその工程で行われるのと同様の値とすることができる。酸素ドナーが生成される熱処理条件であれば良い。例えば、400-500℃程度の熱処理温度のものとすることができる。
熱処理時間tも同様にして適宜決定することができる。
例えば酸素濃度はFT-IRによって測定されるが、その吸収ピークからリファレンスを差し引きした吸光度から酸素濃度に換算する。この時、換算係数はリファレンスによっても異なるし、測定器によっても異なるし、測定器メーカーによっても異なる。従って同じサンプルを測定しても、どの換算係数を用いたかによって変わってくる。また酸素濃度をppmaで表示する測定器メーカーもあれば、atoms/cm3で表示する測定器メーカーもある。
しかしながら、前述したように、近年多く用いられる様になってきた9×1017atoms/cm3(ASTM’79)以下の酸素濃度に対しては、キャリアの生成量をうまく表すことが出来ない。
しかし本手法によれば近年増加しつつある低酸素濃度結晶から従来の酸素濃度結晶に至るまで広く適用することが可能である。従って本手法によって全酸素濃度におけるドナー生成量を求めることが簡便であり、汎用性が高い。
(実験1)
まず、上述した国際公開第2005/071144号等から導かれた関係式:Δ[C]=α’[Oi]3×exp(-β’・D(T)・[Oi]・t) (ここでα’、β’は定数)について検証した。
工程1と同様にして、CZ法及びMCZ法を用いて酸素濃度を振ったP型結晶を育成し、そこからウェーハ状のサンプルを切り出した。
酸素濃度[Oi]=9.2×1017、10.8×1017、12.8×1017、13.8×1017、15.9×1017atoms/cm3(ASTM’79)のサンプルを用意した。
今回はP型のサンプルを用いたので、熱処理前のキャリア濃度から熱処理後のキャリア濃度を差し引いたものを、酸素ドナーに起因するキャリア発生量として求めた。ただし、熱処理後にN型に反転したサンプルにおいては、熱処理前のキャリア濃度と熱処理後のキャリア濃度との和を酸素ドナー起因キャリア発生量とした。これらのキャリア発生量Δ[C]を酸素濃度[Oi]に対してプロットしたのが図9である。
Δ[C]=4.53×10-39×[Oi]3×exp(-1.63×10-5×D(T)・[Oi]・t) …式(1)
[Oi]:酸素濃度(atoms/cm3(ASTM’79))、T:熱処理温度(K)、t:熱処理時間(sec)、D(T):温度Tでの酸素拡散係数(cm2/sec)、k:ボルツマン定数=8.62×10-5(eV/K)
次に、より低酸素濃度領域にまで範囲を広げて式(1)が使用できるのかを確かめた。
実験1と同様に酸素濃度を振ったサンプルを用意した。ただし酸素のレベルは、実験1よりも低く、4.8×1017、5.2×1017、5.8×1017、6.8×1017、8.0×1017atoms/cm3(ASTM’79)である。酸素濃度を下げる必要があるので今回のサンプルは全て磁場を印加したMCZ法を用いて作製した。
またサーマルドナーは酸素析出の核として働くことが同文献内でも報告されており、この高酸素領域ではサーマルドナーから酸素析出物へと成長するため正確な記述ができていなかったとも考えられる。いずれにしても従来の酸素濃度を扱う限りにおいては、式(1)で不都合が無かったと考えられる。
しかしながら、これからは従来になかったような低酸素濃度領域のMCZ結晶が使われていくことが予想されるので、低酸素濃度側もあわせて表記できる式が好ましい。そこで、これらのデータを基に、式(1)に変わる酸素ドナー起因キャリア発生量を求められる式を鋭意検討した。
その結果、実験1、2におけるシリコン単結晶においては、
Δ[C]=5.78×10-74×[Oi]5×exp(-6.25×10-7×D(T)・[Oi]・t) …式(2)
と表せることが判った。
具体的には、図10の低酸素濃度側で実験結果(点)と上記実験1で求められた式(1)のΔ[C]=4.53×10-39×[Oi]3×exp(-1.63×10-5×D(T)・[Oi]・t)(線)とが一致していない。低酸素濃度になると実験値が式(1)より早く小さくなっている。従って式(1)で与えられている酸素濃度の影響度([Oi]3に比例)では弱く、現実はもっと酸素濃度の影響が大きいことが推定される。
そこで、酸素濃度[Oi]の4乗、5乗、6乗に比例すると仮定して、それぞれフィッティングを行ったところ、酸素濃度の5乗に比例すると仮定した場合が最も良い一致が見られた。そのときに求められた係数α、βが式(2)である。
この式(2)と実験1、実験2の結果をともに記載したグラフが図3である。酸素濃度全域にわたって実験結果を良く表すことができている。以上から、酸素ドナー起因キャリアの発生量は式(2)によって求めることが妥当であると考えられる。
以上のようにして、本発明における関係式を導いた。
さらには、キャリア発生量を求めることができるため、これと該当のシリコン単結晶の抵抗率から計算されるキャリア濃度との加算もしくは減算から、熱処理後の抵抗率を推定することができる。
ここで加算もしくは減算と記載したのは、元のシリコン単結晶の導電型に依存するためである。もともとの結晶がN型であれば加算となるし、P型であれば減算を取ることになるからである。更にP型のキャリア濃度よりも酸素ドナー起因キャリアの発生量が多い場合には、N転といわれN型に変化してしまうが、その場合には酸素ドナー起因キャリア濃度からP型キャリア濃度を差し引いた分をN型キャリア濃度として計算することができる。キャリア濃度と抵抗率の関係はアービンカーブを用いて計算することができる。
このようにして、熱処理後のシリコン単結晶について、抵抗率を算出し、評価を行うことができる。
図1に示すような本発明の評価方法をまず行う。
そして、上述したように、予想される低温熱処理後の抵抗率が計算できるので、これを基にして、その低温熱処理を含む該当のプロセスへ投入すべきシリコンウェーハの酸素濃度や抵抗率を定めることが可能である。
CZ法においては、一般に抵抗を制御するためのドーパントをルツボ内に投入した後に結晶を育成するが、この際にドーパントは偏析現象によって結晶のトップ側とボトム側で抵抗率が変化する。顧客に出荷する際には要求を満たす部分を出荷することになる。従って要求の抵抗率範囲が狭ければ、製品長さが短くなる。
そして、当初の予定通りのプロセスを経て、所望のシリコンウェーハを得ることが可能である。
(実施例1)
実験2で用いたサンプルに加え、酸素濃度が2.9~8.9×1017atoms/cm3(ASTM’79)である低酸素濃度サンプルを用意した。P型に限らずN型のサンプルも含まれている。
これらのサンプルについて、本発明における関係式(この場合、式(2))を用い、酸素ドナー起因のキャリアの発生量を算出して評価した。
450℃の熱処理時間が1時間と15時間の場合だけでなく、5時間と10時間の場合についても評価した。
関係式で得られるグラフを、各熱処理時間ごとに図4に示す。
なお、N型のサンプルの場合には熱処理後の抵抗率から求められるキャリア濃度から、熱処理前の抵抗率から求められるキャリア濃度を引いたものを発生量とした。
P型で1000Ωcmから2000Ωcmの抵抗率のウェーハが要求された。また、このデバイス最終段階で行われる低温の熱処理は450℃で2時間に相当するプロセスである。そこで、この目標を達成するために検討を行った。
結晶の製造はMCZ法にて行い、ルツボのサイズが26インチ(66cm)である装置を用いて結晶育成を行うこととした。
先に述べた様に、結晶トップ側の酸素濃度は下がりにくい。例えば図2の装置を用い、酸素濃度[Oi]を4×1017atoms/cm3(ASTM’79)狙いとした場合と、8×1017atoms/cm3(ASTM’79)狙いとした場合とを比較すると、酸素濃度に関する不良率が、4×1017atoms/cm3(ASTM’79)狙いでは、8×1017atoms/cm3(ASTM’79)狙いの2倍から3倍となりコストアップになる。従って狙うべき酸素濃度が高い方ほど不良率が下がってコストも低下する。しかしながら、酸素濃度を高くすると酸素ドナー起因キャリアが発生してしまい、所望の抵抗率に入らない。
そこで本発明における関係式(この場合、式(2))を用いて試算を行った。
そして、試算した酸素濃度[Oi]が4×1017、5×1017、6×1017、7×1017atoms/cm3(ASTM’79)及び酸素濃度[Oi]が0atoms/cm3(ASTM’79)の場合のキャリア発生量に基づいて、上記低温熱処理後で、酸素ドナー起因のキャリアが発生した際の結晶長さ方向の抵抗率分布を、各酸素濃度ごとに、図6にプロットした。
この図6では、横軸は結晶の固化率(=結晶重量/初期原料重量)で表している。
酸素濃度[Oi]が5×1017atoms/cm3(ASTM’79)を狙った場合にはデバイス工程後に約半分が規格外になり、また、6×1017、7×1017atoms/cm3(ASTM’79)を狙った場合にはほぼ全量が規格外になってしまうことが容易に判断できる。
実施例2と同様に、デバイス最終段で行われる低温の熱処理が450℃で2時間相当であり、P型で1000Ωcmから2000Ωcmの抵抗率のウェーハが要求された。
まず、実施例2の図6のグラフから、上記規格内の抵抗率のウエーハを得るには、シリコン単結晶の育成のときに酸素濃度[Oi]が4×1017atoms/cm3(ASTM’79)を狙えばよいことが示唆された。この酸素濃度でシリコン単結晶を育成し、上記低温熱処理のプロセスを行えば、図6における酸素濃度[Oi]が4×1017atoms/cm3(ASTM’79)のときの抵抗率を有するものが得られると考えられる。
そこで、ここでは、図6を踏まえ、さらには無理なく酸素濃度を下げられる条件で結晶を育成した場合の酸素濃度から狙うべき抵抗率を定めて、製品が少しでも多く取れる設計を行うこととする。実施例2と同様の製造装置を用い、無理のない条件で低酸素濃度化を狙った場合には、図7のような酸素濃度プロファイルが得られる。
上述の考慮を行った結果、狙うべき抵抗率はトップ側で約1350Ωcmであった。更に上述の酸素濃度から計算されるキャリア発生量を考慮し、デバイス工程後に予想される抵抗率も図8に破線で示した。
そして、この設計を基にしてシリコン単結晶を育成した。また、育成した結晶からウェーハ状のサンプルを切り出し、ドナーキラー熱処理を施し抵抗率を測定した。その結果、図8の実線と一致する抵抗率が得られた。
その結果、抵抗率のプロファイルは、式(2)から求めたデバイス熱処理後に予想される抵抗率プロファイルの図8の破線に一致する結果が得られた。またこれらの結晶(の全ての領域)から切り出された製品ウェーハを実デバイス工程に投入して評価してもらった結果、デバイス動作に問題ないことが確認された。
実施例3と同様の要求に対して、本手法を用いずに結晶を育成することとした。
酸素ドナー起因のキャリアの発生量を考慮することなく、抵抗率規格が1000Ωcmから2000Ωcmなので、結晶のトップ側で1900Ωcmとなる様に狙い抵抗率を定めた。この狙いから計算される抵抗率を図8に一点鎖線で示した。
また酸素濃度は実施例3と同様のプロファイルとした。
その結果、図8の一点鎖線にほぼ乗るように抵抗プロファイルが得られた。この時点では抵抗率規格1000~2000Ωcmを満たしており合格品である。
その結果、抵抗率のプロファイルは、式(2)から求めたデバイス熱処理後に予想される抵抗率プロファイルの図8の点線と同等の分布を示した。
つまり、酸素ドナー起因のキャリア発生量を考慮せずに結晶を育成した結果、デバイス工程後も規格を満たす製品の長さは固化率が0.25~0.7までとなり、実施例3で得られた0.11~0.7に比較して製品長さが減少してしまった。
Claims (4)
- シリコン単結晶の評価方法であって、
シリコン単結晶に熱処理を施したときに生成される酸素ドナーを起因とするキャリアの発生量Δ[C]を、
前記シリコン単結晶中の酸素濃度[Oi]、前記熱処理の温度T、前記熱処理の時間t、温度Tでの酸素拡散係数D(T)とから、
Δ[C]=α[Oi]5×exp(-β・D(T)・[Oi]・t) (ここでα、βは定数)
の関係式を用いて算出して評価することを特徴とするシリコン単結晶の評価方法。 - 前記評価するシリコン単結晶中の酸素濃度を、9×1017atoms/cm3(ASTM’79)以下とすることを特徴とする請求項1に記載のシリコン単結晶の評価方法。
- 前記関係式を用いて酸素ドナー起因のキャリアの発生量を算出し、該算出したキャリアの発生量を用いて、前記熱処理後のシリコン単結晶の抵抗率を算出して評価することを特徴とするシリコン単結晶の評価方法。
- 請求項3に記載のシリコン単結晶の評価方法を用いて前記熱処理後のシリコン単結晶の抵抗率を算出し、該算出した抵抗率に基づいて、シリコン単結晶を育成するときの酸素濃度および抵抗率の狙い値を決定し、該決定した狙い値に基づいてシリコン単結晶を育成することを特徴とするシリコン単結晶の製造方法。
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JP6036670B2 (ja) * | 2013-12-10 | 2016-11-30 | 信越半導体株式会社 | シリコン単結晶基板の欠陥濃度評価方法 |
WO2015186288A1 (ja) * | 2014-06-02 | 2015-12-10 | 株式会社Sumco | シリコンウェーハおよびその製造方法 |
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JP2019019030A (ja) * | 2017-07-18 | 2019-02-07 | 信越半導体株式会社 | シリコン単結晶の評価方法およびシリコン単結晶の製造方法 |
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