KR100693917B1 - Silicon single crystal - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon single crystal and a silicon single crystal production apparatus, wherein, in a silicon single crystal manufactured by Czochralski method, by suppressing aggregated three-dimensional crystal defects by controlling the concentration of impurities other than silicon below a predetermined range, The present invention provides a silicon single crystal characterized in that not only intrinsic point defects but also foreign point defects are controlled. Further, in the silicon single crystal manufacturing apparatus, a silicon single crystal manufacturing apparatus using a high temperature quartz crucible capable of preventing foreign defects, and using a hot zone coated with a SiC film on its surface is provided. As described above, the present invention can determine the crystal defects of the impurities injected into the single crystal silicon, and control the concentration of the impurities to provide a silicon single crystal having few crystal defects due to the impurities.

Foreign Defects, COP, LDP, Public Defects, Inherent Defects, Impurity Concentration

Description

Silicon single crystal             

1 is an X-ray topography for explaining the point defect behavior according to barium ions according to the first experimental example of the present invention.

Figure 2 is an X-ray topography for explaining the point defect behavior according to the phosphorus ion in accordance with the second experimental example of the present invention.

3 is an X-ray topography for explaining the point defect behavior according to phosphorus and aluminum ions according to the third experimental example of the present invention.

4 is an X-ray topography for explaining the point defect behavior according to the nitrogen ion according to the fourth experimental example of the present invention.

5 is an X-ray topography for explaining the point defect behavior according to carbon ions according to the fifth experimental example of the present invention.

6 is a cross-sectional view showing the interior of the silicon single crystal ingot growth apparatus according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10 chamber 20 quartz crucible

25: crucible support 30: rotating shaft

40: heater 45: thermos

50: heat sheet 60: heat shield

65: through hole

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to silicon single crystals and wafers and apparatuses for manufacturing the same, and more particularly, to silicon single crystals and wafers in which intrinsic and foreign defects are controlled.

In recent years, as the design rule is gradually miniaturized with high integration of semiconductor circuits, the insulating oxide film of the gate electrode portion is becoming thinner. Accordingly, even in a thin insulating oxide film, a silicon wafer having a high insulation breakdown voltage and a small leakage current during a device element operation is required. In other words, there is an increasing demand for a silicon wafer substrate having excellent oxidation resistance characteristics of a gate oxide film. In recent years, it has been found that the cause of lowering the oxide dielectric breakdown voltage is closely related to the crystal defects present in the silicon wafer. Crystal defects include three-dimensional crystal defects, COP, LDP, and oxygen precipitation.

Crystal Originated Particle (COP) refers to surface crystal defects, and is one of crystal defects generated during crystal growth. Void defects of an octahedral structure in which vacancy point defects are aggregated during cooling of crystals are formed. One form of defects is defects revealed on the surface by sliced wafers from single crystals. That is, defects in the voids are defects that are exposed on the wafer surface of the aggregated three-dimensional voids.

In addition, the large dislocation pi (LDP) is one of crystal defects generated during crystal growth, and is a dislocation-loop formed by aggregation of self-interstitial point defects. In other words, the intrusion type defect is a dislocation defect in the form of an aggregated rope.

Oxygen precipitates are three-dimensional defects in which interstitial oxygen mixed into silicon single crystals during crystal growth appears as bulk microdefects as nucleation and growth mechanisms through further heat treatment of wafers or single crystals.

As described above, in order to control crystal defects such as three-dimensional crystal defects, COP, LDP, and oxygen precipitation of silicon single crystals, it is very important to control the concentration of point defects present in the crystals.

Therefore, in order to control crystal defects such as COP and LDP, which appear as defects on silicon wafers, a method of controlling high temperature behavior of intrinsic point defects (Vorokov theory) has been studied. That is, the intrinsic point defects change depending on the crystal growth conditions (V / G). Here, V denotes a growth rate, and G denotes a crystal axial temperature gradient, and the intrinsic defects can be controlled by the growth rate and temperature of the silicon crystal.

However, through the research of the present inventors, not only the intrinsic defects due to nucleation and growth mechanisms during the cooling of crystals contribute to the occurrence of aggregation, but also the presence of extrinsic point defects due to the incorporation of impurities. It has been found to affect the generation behavior of defects. Therefore, it is not possible to sufficiently control the desired crystal defects without controlling the concentration of impurities other than silicon which causes such foreign defects. That is, it is impossible to ignore the crystal defects caused by the extraneous defects caused by certain impurity atoms added during silicon crystal growth. Outpatient defects are detailed in Thermodynamics of Materials Vol. 2 (David V. Ragone, MIT Series, John Wiley & Sons Inc, PP68-75).

Conventionally, impurity atoms are arbitrarily added or controlled for specific purposes. As such impurity atoms, nitrogen (N), carbon (C), barium (Ba), and group 3 and 4 elements, which are dopants for resistance control, were added.

These impurities have a problem that unwanted crystal defects are additionally generated due to the intrinsic extraneous defect defects at certain concentrations due to their own characteristics.

Accordingly, the present invention provides a silicon single crystal and its manufacturing apparatus which eliminate the crystal defects due to foreign defects by analyzing the effect of crystal defects through the addition test of various impurity atoms other than silicon in order to solve the above problems. For that purpose.

In the silicon single crystal produced by the Czochralski method according to the present invention, aggregated three-dimensional crystal defects are suppressed by controlling the concentration of impurities other than silicon below a predetermined range, and not only intrinsic defects but also foreign defects are controlled. A silicon single crystal is provided.

Here, it is preferable to use an element which reacts with bacon as an impurity or suppresses the generation of foreign bacon. In addition, it is preferable to use an element which reacts with the self-interstial as the impurity or which suppresses the generation of the foreign self-interstial.

At this time, it is effective that barium is used as the impurity, and the concentration at this time is 10 ⁸ / cm 3 or less. In addition, it is effective to use aluminum as the impurity in phosphorus-doped N-type silicon, and the aluminum is injected at a concentration of 10 ¹³ / cm 3 or less. Further, it is effective that nitrogen is used as the impurity, and the concentration at this time is 10 ¹² / cm 3 or less. It is also effective that carbon is used as the impurity, and the concentration at this time is 10 ¹⁴ / cm 3 or less.

Furthermore, in the silicon wafer which concerns on this invention, the silicon wafer formed by processing the silicon single crystal of any one of Claims 1-3 is provided.

In addition, in the silicon single crystal manufacturing apparatus according to the present invention, a silicon single crystal manufacturing apparatus using a high-purity quartz crucible capable of preventing foreign defects, and using a hot zone coated with a SiC film on the surface.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like numbers refer to like elements in the figures.

In the present invention, the effect of the impurity on the caking defect through the experiment for each impurity element added to the silicon crystal was identified. In addition, growth stop experiments were conducted to accurately determine the effect of each impurity element on the caking defect behavior.

As a comparison target, a boron (B) -doped silicon single crystal was used, and the added boron concentration was 2 to 4 × 10 ¹⁵ / cm 3. The concentration of the impurity added was 10 ⁹ to 10 ¹⁷ / cm 3 in consideration of the solubility of each element in order to clearly identify the effect. A silicon single crystal 6 inches (150 mm) in diameter was used.

In addition, in the growth stop experiment, the single crystal ingot was pulled to 0.9 mm / min. The growth was stopped and maintained for 50 to 70 minutes at the 50 to 70 cm position during the growth, and then the pulling started again to 0.9 mm / min. After completion of growth, the single crystal ingot was vertically cut and subjected to oxygen precipitation heat treatment. Oxygen precipitation heat treatment was performed for about 3 to 5 hours at a temperature of about 700 to 900 degrees, and then for 14 to 18 hours at a temperature of 900 to 1100 degrees. Since the oxygen precipitation behavior is significantly influenced by the concentration of bacon and interstitial, it is possible to indirectly grasp the concentration distribution of point defects. The heat-treated wafers were examined by X-ray topography to determine the distribution of oxygen precipitation.

1 is X-ray topography for explaining the point defect behavior according to barium ions according to the first experimental example of the present invention.

FIG. 1A is an X-ray topography of a reference silicon single crystal, and FIG. 1B is an X-ray topography of a silicon single crystal with Ba added at a concentration of 1.3 to 2.5 × 10 ⁹ / cm 3.

Ba is coated on the crucible wall in the form of BaCO ₃ or added to the silicon solution to improve the silicon single crystallization rate. The added Ba can promote the devitrification of the quartz crucible wall to prevent the polycrystallization factor from falling out of the crucible wall. In this experimental example, the point defect of the silicon single crystal in which Ba was injected at a predetermined concentration was measured.

Ba has generally been thought to have a significantly larger co-radius compared to silicon, so that the amount incorporated into the crystal can be neglected because of its low solubility in silicon. However, the results of this experiment show that the addition of concentrations below the detection limit of the impurity measurement equipment has a significant effect on the point defect behavior in silicon.

As shown in FIG. 1, when Ba is added at a specific concentration or higher, foreign point defects are induced and unwanted crystal defects are generated. In other words, due to the incorporation of Ba impurities, the concentration of the empty point defects increased (FIG. 1B). It can be seen that even a small amount of Ba provides a favorable environment in which void defects are generated in the silicon crystal lattice due to the shared radius (1.38 Å) is larger than the silicon's shared radius (1.17 Å) (1.18 times). In addition, since Ba has a higher fraction of BaO in the single crystal ingot than Ba silicon alone, it causes a large stress in the silicon crystal lattice, so that the silicon crystal at the grain growth interface is relaxed. This is due to an increase in the initial extrinsic Vacancy concentration incorporated in.

Therefore, the amount of Ba added to the silicon single crystal wafer must be properly adjusted. Therefore, the concentration of Ba should be controlled to 1.3 × 10 ⁹ / cm 3 or less, and this crystal defect was reduced to some extent by controlling the concentration of Ba to 10 ⁸ / cm 3. As a result, in order to produce a silicon single crystal with few crystal defects, it is preferable to control the concentration of Ba mixed in the silicon crystal to 10 ⁸ / cm 3 or less, more preferably 10 ⁷ / cm 3 or less.

2 is an X-ray topography for explaining the behavior of point defects due to phosphorus ion addition according to a second experimental example of the present invention.

FIG. 2A is an X-ray topography of a reference silicon single crystal, and FIG. 2B is an X-ray topography of a silicon single crystal with P added at a concentration of 0.5 × 10 ¹⁵ / cm 3 to 1.0 × 10 ¹⁵ / cm 3.

P is added to the silicon single crystal wafer to control the wafer's resistance. In other words, when P is added, free electrons become N-type semiconductors, which become major carriers. In this experiment, we investigated the point defect behavior according to the amount of P injected.

As shown in FIG. 2, P is 0.94 times smaller than the silicon (1.10Å) of the shared radius size, but the stress generation effect due to the presence of P impurities is relatively high at a high temperature near the initial crystal growth interface due to the position of P atoms in the substitutional sites. Since it is small, it can be seen that the effect on foreign adjunct in the high temperature region is negligibly small. However, P increases the Fermi-Energy Level by providing free electrons in the silicon lattice structure. Therefore, such a change in Fermi energy can be incorporated into a relatively high concentration of bacon defects compared to the silicon single crystal (Fig. 2b). When boron (B) is added, it can be understood that by providing a hole, a change in Fermi energy level creates an environment in which magnetic intrinsic point defects can be incorporated at a high concentration as opposed to when P is added.

3 is X-ray topography for explaining the point defect behavior according to the phosphorus and aluminum ions according to the third experimental example of the present invention.

3A is an X-ray topography of a reference silicon single crystal, FIG. 3B is an X-ray topography of a silicon single crystal with P added at a concentration of 0.5 × 10 ¹⁵ / cm 3 to 1.0 × 10 ¹⁵ / cm 3, and FIG. 3C is a silicon single crystal of FIG. 3B. X-ray topography of a silicon single crystal to which Al is added in a concentration of 1.0 × 10 ¹⁵ / cm 3 to 2.0 × 10 ¹⁵ / cm 3.

As shown in FIG. 3, it can be seen that the point defect behavior is canceled by adding Al to the silicon-doped P-added silicon single crystal. In other words, the expansion of bacon due to the addition of P was offset by the addition of Al. As Al is present in the silicon crystal lattice structure as a substitutional site of silicon atoms, the effect of lattice stress generation is very small, but the mixing effect of P impurity that supplies free electrons and the Fermi energy level of Al impurity that supplies holes The effects on each other cancel each other out so that the generation of foreign defects is suppressed. Therefore, in the case of N type silicon implanted with P to reduce foreign defects, it is effective to inject Al. That is, it is effective to inject the concentration of Al to 1.0 × 10 ¹⁵ / cm 3 to 2 × 10 ¹⁵ / cm 3 or less. In addition, when P is injected, the concentration of Al is preferably controlled to 10 ¹³ / cm 3 or less, more preferably 10 ¹² / cm 3 or less.

4 is an X-ray topography for explaining the point defect behavior according to the nitrogen ion according to the fourth experimental example of the present invention.

4A is an X-ray topography of a reference silicon single crystal, FIG. 4B is an X-ray topography of a silicon single crystal with N added at a concentration of 2.0 × 10 ¹³ / cm 3 to 4.0 × 10 ¹³ / cm 3, and FIG. 4C is 1.0 × 10 with N ¹⁴ / ㎤ to 2.0 × 10 ¹⁴ / of the silicon single crystal was added to ㎤ density and X-ray topography, Figure 4d is N is 2.0 × 10 ¹⁴ / ㎤ to 4.0 × 10 ¹⁴ / ㎤ concentration of the silicon single crystal X-ray topography of the added 4E is an X-ray topography of a silicon single crystal in which N is added at a concentration of 0.5 × 10 ¹⁴ / cm 3 to 1.0 × 10 ¹⁴ / cm 3.

As shown in FIG. 4, it can be seen that the interstitial region continues to shrink as the amount of nitrogen added increases. This is because nitrogen is present in the lattice sites in the silicon lattice structure in the crystal or in the form of N ₂ V or the like by interacting with vacancy, thereby increasing the concentration of foreign voids. Nitrogen also reduces the diffusion rate of public defects by combining with them, resulting in increased concentrations of residual vacancy due to inhibition of nucleation and growth of voids and consequently coarse oxygen precipitation that promotes residual vacancy concentrations. The formation of nuclei is promoted. Thus, increased oxygen precipitation and OiSF act as large defects in the device active area and must be controlled to improve device yield and performance.

Therefore, the concentration of N should be 2 × 10 ¹³ / cm 3 to 4 × 10 ¹³ / cm 3 or less, and when controlled to 10 ¹² / cm 3 or less, crystal defects were somewhat reduced. Therefore, it is preferable to control the concentration of N to 10 ¹² / cm 3 or less. More preferably, the concentration of N is controlled to 10 ¹¹ / cm 3 or less.

5 is X-ray topography for explaining the point defect behavior according to the carbon ions according to the fifth experimental example of the present invention.

5A is an X-ray topography of a reference silicon single crystal, and FIG. 5B is an X-ray topography (C) of a silicon single crystal in which C is added at a concentration of 4.0 × 10 ¹⁶ / cm 3 to 7.0 × 10 ¹⁶ / cm 3. exist. This is because C is a group 4 element, such as Si, and is located at the substitution site. However, C has a very small share radius of 0.65 times larger than that of Si. Therefore, due to the incorporation of C, stress is generated in the silicon crystal lattice structure, and thus it is considered that the intrinsic intrinsic defect concentration increases at high temperature near the initial crystal growth interface. As the crystal cools, in the relatively low temperature region below 1200 ° C, the concentration of the equilibrium foreign intrinsic defect increases, thereby facilitating the generation of LDP crystal defects. In addition, the C impurity may promote the generation of oxygen precipitates in the temperature range of 900 to 1100 degrees, which may ultimately lead to deterioration of the device function. Therefore, the concentration of C should be 4 × 10 ¹⁶ / cm 3 to 7 × 10 ¹⁶ / cm 3 or less. Therefore, when the concentration of C is injected at 10 ¹⁴ / cm 3 or less, crystal defects can be reduced to some extent, so it is preferable to control the concentration of C at 10 ¹⁴ / cm 3 or less. Furthermore, it is more preferable to control the concentration of C to 10 ¹³ / cm 3 or less.

As described above, in the present invention, the concentration distribution of foreign point defects is tested according to the concentration of external impurities injected into the silicon single crystal, and the concentration of the external impurities injected into the silicon single crystal is adjusted to a predetermined range or less.

That is, it is preferable to control the concentration of Ba to 10 ⁸ / cm 3 or less, more preferably 10 ⁷ / cm 3 or less. In the case of P-doped N-type silicon, it is preferable to control the concentration of Al to 10 ¹³ / cm 3 or less, more preferably 10 ¹² / cm 3 or less. In addition, it is preferable to control the concentration of N to 10 ¹² / cm 3 or less, and more preferably to control 10 ¹¹ / cm 3 or less. The concentration of C is preferably controlled to 10 ¹⁴ / cm 3 or less, more preferably 10 ¹³ / cm 3 or less.

As described above, it is possible to prepare a silicon single crystal rod having no three-dimensional crystal defects aggregated and controlled as well as inherent defects of silicon single crystals. In addition, silicon wafers with controlled intrinsic and foreign defects can be manufactured. This can be obtained by sufficiently controlling the concentration of impurities other than silicon causing intrinsic point defects in addition to intrinsic point defects such as vacancy and self-interstial during crystal growth. Here, it is preferable to use an element which can control the presence of foreign vacancy due to the presence of a controlled impurity reacts with vacancy or its size is larger than the silicon covalent radius. Alternatively, it is preferable to use an element which is capable of suppressing the generation of foreign self-interstital due to the presence of the controlled impurity in reaction with the self-interst or its size smaller than the silicon covalent bond radius.

These concentrations of impurities can be determined by the Czochralski method for growing silicon single crystal rods, polycrystalline silicon, which is a raw material of silicon single crystal ingots, quartz crucibles containing silicon melts, and various graphite hot zones (polycrystals) surrounding the crystal growth system. And regions except for silicon and quartz crucibles). Therefore, the purity of the polycrystalline silicon and quartz crucible as the raw material should be adjusted. At this time, the purity of the polycrystalline silicon and quartz crucible is preferably a concentration that can control the concentration of the above-mentioned impurities below the above-mentioned range. That is, high purity polycrystalline silicon and quartz crucibles are required. In particular, the concentration control management below the significance level is required for the elements affecting the foreign defects as described above. In addition, since the graphite hot zone surrounding the system is generally a carbon (C) material, a large amount of C should be prevented from being incorporated into the silicon melt or other impurities present in the hot zone surface. For this purpose, it is preferable to coat SiC of a predetermined thickness.

In the present invention, a silicon single crystal ingot is grown according to the Czochralski method, and a silicon single crystal ingot growth apparatus as shown below is used.

6 is a cross-sectional view showing the inside of the silicon single crystal ingot growth apparatus according to the present invention.

Referring to FIG. 6, the apparatus for manufacturing a silicon single crystal ingot according to the present invention includes a chamber 10, and growth of the silicon single crystal ingot is performed in the chamber 10.

The quartz crucible 20 containing the silicon melt SM is installed in the chamber 10, and the crucible support 25 made of graphite is installed outside the quartz crucible 20 so as to surround the quartz crucible 20. do.

The crucible support 25 is fixedly installed on the rotary shaft 30, which is rotated by a driving means (not shown) to raise the crucible 25 while rotating the quartz-liquid interface at the same height. Keep it. The crucible support 25 is surrounded by a cylindrical heater 40 at predetermined intervals, and the heater 40 is surrounded by a thermos 45.

The heater 40 melts a high-purity polysilicon mass loaded in the quartz crucible 20 to form a silicon melt SM. The thermostat 45 has heat from the heater 40 toward the wall of the chamber 10. Prevents diffusion and improves thermal efficiency.

In the upper part of the chamber 10, a pulling means (not shown) for winding and pulling a cable is provided. The lower part of the cable 10 is in contact with the silicon melt SM in the quartz crucible 20 and pulled up to form a single crystal ingot ( A seed crystal for growing IG) is installed. The pulling means rotates while pulling up the cable during the growth of the single crystal ingot IG, wherein the silicon single crystal ingot IG is rotated about the same axis as the rotation axis 30 of the crucible 20. Rotate in the opposite direction to the direction of pulling up.

In the upper portion of the chamber 10, an inert gas such as argon (Ar), neon (Ne), and nitrogen (N) is supplied to the grown single crystal ingot (IG) and the silicon melt (SM). Discharge through the bottom of the chamber (10).

A heat shield 50 is installed between the silicon single crystal ingot IG and the crucible 20 so as to surround the ingot IG to block heat radiated from the ingot, and the heat shield 50 with the ingot IG. The heat shield 60 is attached to the closest part to further block heat flow to preserve heat.

A silicon united ingot is produced using the above-described ingot growth apparatus. That is, the raw material for ingot production is placed in a quartz crucible (grower), and then melted at a high temperature to make a liquid state, and then grown into a single crystal rod. Analyze whether the grown single crystal rods are suitable for the desired characteristics. The single crystal rods thus processed are sliced to a certain thickness to form a wafer. The lapping process removes damage to the wafer surface generated during the slicing process, makes the thickness and flatness of the wafer uniform, and then removes the remaining damage on the wafer surface using a chemical solution. Thereafter, the heat treatment process may have an original resistivity of the crystal. Next, the wafer surface roughened through the polishing process is polished to have a high degree of flatness. Through the process as described above, it is possible to produce a silicon wafer controlled not only inherent defects but also foreign defects according to the present invention.

As described above, the present invention can determine the crystal defects of the impurities injected into the single crystal silicon, and control the concentration of the impurities to provide a silicon single crystal with less crystal defects caused by the impurities.

Claims (9)

In the silicon single crystal produced by the Czochralski method, As an impurity other than silicon, barium may be adjusted to a concentration of 10 ⁸ / cm 3 or less, nitrogen to 10 ¹² / cm 3 or less, carbon to 10 ¹⁴ / cm 3 or less, or phosphorus doped N-type silicon In this case, the aggregated three-dimensional crystal defects are suppressed by controlling the aluminum to a concentration of 10 ¹³ / cm 3 or less, and silicon single crystals are controlled as well as foreign defects. The method according to claim 1, A silicon single crystal using an element which reacts with vacancy as the impurity or suppresses the generation of foreign vacancy. The method according to claim 1, A silicon single crystal using an element which reacts with a self-interstital as an impurity or suppresses the generation of a foreign self-interstital. delete delete delete delete In a silicon wafer, The silicon wafer formed by processing the silicon single crystal of any one of Claims 1-3. In the silicon single crystal manufacturing apparatus, Adjust barium to a concentration below 10 ⁸ / cm 3, adjust nitrogen to 10 ¹² / cm 3 or below, carbon to 10 ¹⁴ / cm 3 or below, or phosphorus-doped N-type silicon to 10 ¹³ An apparatus for producing a silicon single crystal, which uses a high-purity quartz crucible that can be prevented from foreign defects by adjusting to a concentration of / cm 3 or less, and a SiC film-coated hot zone.

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