KR20070075429A - Method for controlling oxygen content in silicon single crystalline ingot, ingot produced thereby - Google Patents

Abstract

A method for controlling the oxygen density of a silicon single crystalline ingot is provided to smoothly adjust the density of oxygen by adjusting the rotation speed of a quartz crucible while using AC power. A crucible containing a silicon melt is included in a silicon single crystalline ingot growing apparatus equipped with a heater using AC current. The rotation speed of the crucible is adjusted to control the density of oxygen gushing out from the crucible and the convection of a silicon melt so that a single crystalline ingot and a wafer having various specifications of an oxygen density are fabricated.

Description

TECHNICAL FOR CONTROLLING OXYGEN CONTENT IN SILICON SINGLE CRYSTALLINE INGOT, INGOT PRODUCED THEREBY}

The present invention relates to a method for producing a silicon single crystal ingot by the Czochralski method, and more particularly, to a method for adjusting the oxygen concentration of a silicon single crystal ingot, an ingot and a wafer manufactured using the same.

In general, in the method of growing a silicon single crystal ingot according to the Czochralski method, polycrystalline silicon is loaded into a quartz crucible and melted polycrystalline silicon with heat radiated from a heater to form a silicon melt, and then a silicon single crystal ingot from the surface of the silicon melt. To grow.

When growing a silicon single crystal ingot, the crucible is raised while rotating the shaft supporting the crucible so that the solid-liquid interface is maintained at the same height. Rotate to and pull up. The grown silicon single crystal ingot goes through a wafer processing process such as slicing, lapping, polishing, and cleaning to become a silicon single crystal wafer to be used as a semiconductor device substrate.

Oxygen corresponding to light element impurity in silicon single crystal ingot growth is dissolved into silicon melt on the inner surface of quartz crucible where silicon melt and quartz crucible are contacted. More than about 98% of oxygen evaporates into SiO-type gas on the surface of silicon melt. Oxygen present near the interface between the single crystal ingot and the silicon melt is incorporated into the silicon single crystal ingot grown by segregation.

Oxygen in silicon crystals has both positive and negative sides. Oxygen present in the bulk of the silicon wafer is known to be essential for the operation of the semiconductor device because it acts as an intrinsic gettering site to remove metal impurities that may be generated by subsequent semiconductor device manufacturing processes. Oxygen may deteriorate electrical characteristics of the semiconductor device by causing defects such as precipitates, dislocations, and stacking defects during the heat treatment process of the semiconductor device manufacturing process.

Therefore, ultimately, the oxygen content in the silicon crystal is a very important factor in terms of quality control, which must be very carefully controlled according to the requirements of the silicon wafer application field.

Since the early 1980s, the oxygen concentration of silicon crystals grown by the Czochralski method used in industrially dominant positions varies with the length of the crystal, which is higher at the seed end than at the middle and / or bottom of the crystal. . The oxygen concentration also changes along the radial direction of the crystal cross section.

In US Pat. No. 4,436,577, Frederich et al. Present a method for controlling oxygen content and its distribution in silicon crystal rods prepared by the action of seed crystals on molten silicon held in a (silica-> quartz) crucible. It was. In this method, the oxygen seed distribution was controlled by rotating the crystal seed rod at a higher rotational speed in the opposite direction to the rotational direction of the crucible as it was pulled from the melt, while increasing the rotational speed of the crucible when the melting level of the crucible was reduced. .

Recently, however, advances in silicon semiconductor technology have required silicon crystals of larger diameter than those disclosed in US Pat. No. 4,436,577. This increased the melt charge amount and required a larger crucible diameter.

On the other hand, because of the physical constraints imposed to optimize the rotational speed of crystals and crucibles for stable crystal growth, it has become increasingly difficult to homogenize oxygen content to the desired concentration range.

As one solution for overcoming the difficulty of adjusting the oxygen concentration, attention has recently been focused on using a radial cusp magnetic field that is axially symmetric. This method is presented in Japanese Patent Laid-Open No. 58-217493. According to this method, a pair of coils in which circular currents flow in opposite directions is disposed above and below the melt. As a result, a radial horizontal magnetic field is formed at the 1/2 position along the length of the melt, and the radial cusp magnetic field restricts and stabilizes the flow of the melt to prevent contamination from the crucible.

In addition, Barraclough et al. In WO 89/08731 (89. 9. 27) proposed an improvement of the cusp magnetic field method. According to WO 89/08731, the magnetic field component parallel to the axis of rotation of the crystal grows to be less than 500 gauss at the interface of the melt and more than 500 gauss at other parts of the melt, and such a magnetic field distribution is determined. It must be maintained during growth.

In addition, Hirata et al. Proposed another improved method in Japanese Patent Application Laid-Open No. 1-282185. According to this, moving impurities such as oxygen can be controlled by varying the ratio of the strength of the magnetic field component that cuts the surface of the melt vertically by giving a cusp magnetic field to the melt and the strength of the storage component that cuts the bottom of the melt vertically. have. The above ratio can be changed by (1) moving the coil with respect to the crucible (coil distance is kept constant), (2) changing the ampere turn ratio of the coil days, or (3) changing the distance between the coil days.

However, none of the cusp field methods disclosed to date is completely satisfactory, and under certain conditions, there is a disadvantage that the oxygen uniformity in the axial direction and the radial direction deteriorates similarly to that observed when using the axial field.

Therefore, the inventors of the present invention studied the effects on the quartz crucible rotation speed and the oxygen concentration in the silicon single crystal ingot by using an ingot growth apparatus equipped with a heater using AC current to solve the problems of the prior art as described above. When the crucible rotation speed is lower than 2rpm, the ingot growth apparatus having a graphite heating element using DC current, which is generally used for silicon single crystal ingot growth, tends to decrease oxygen concentration as the quartz crucible rotation speed decreases. Unlike the ingot growth apparatus provided with a heater using an AC current, it was confirmed that the oxygen concentration of the silicon single crystal ingot was easily controlled, and thus the present invention was completed.

Therefore, the main object of the present invention is to provide a method for controlling the oxygen concentration of a silicon single crystal ingot pulled up by a seed crystal from a silicon melt contained in a quartz crucible.

In particular, the present invention provides a method for controlling the oxygen concentration of a silicon single crystal ingot by controlling the crucible rotation speed using an ingot growth apparatus equipped with an AC heater.

Another object of the present invention is to provide a high quality silicon single crystal ingot growth method in which the oxygen concentration is controlled in various ways.

Another object of the present invention is to provide a high productivity silicon single crystal ingot growth method.

It is another object of the present invention to provide a silicon single crystal ingot growth method with high acquisition yield.

It is still another object of the present invention to provide a silicon single crystal ingot and a wafer in which the oxygen concentration is controlled in various ways according to a specification desired by a customer.

In order to achieve the object of the present invention described above, the present invention is a method for adjusting the oxygen concentration of a silicon single crystal ingot grown by Czochralski method, the oxygen eluted from the crucible by controlling the rotational speed of the crucible containing the silicon melt It provides a method for adjusting the oxygen concentration of a silicon single crystal, characterized in that the concentration is controlled.

The amount of dissolved oxygen is controlled by providing a heater using an AC current.

In addition, the present invention is a silicon single crystal ingot grown by the Czochralski method, in which the silicon single crystal ingot grown by controlling the rotational speed of the crucible containing the silicon melt of the silicon single crystal ingot growth apparatus equipped with a heater using AC current. A silicon single crystal ingot having an oxygen concentration of 8 pma or more and 17 ppma or less is provided.

In addition, the present invention is a silicon wafer manufactured from a silicon single crystal ingot grown by Czochralski method by controlling the rotational speed of the crucible containing the silicon melt of the silicon single crystal ingot growth apparatus with a heater using AC current, The wafer provides a silicon wafer characterized in that the interstitial oxygen concentration is 8 ppm or more and 17 ppm.

In addition, the present invention is an apparatus for growing a silicon single crystal by the Czochralski method, comprising: a chamber; A crucible installed inside the chamber and containing a silicon melt; A heater installed on the side of the crucible to heat the silicon melt and using AC current; And an pulling mechanism for pulling up the silicon single crystal grown from the silicon melt.

Oxygen concentration control method of the silicon single crystal ingot according to the present invention, the ingot and wafer prepared using the same has the following effects.

According to the oxygen concentration adjusting method of the silicon single crystal ingot of the present invention, the oxygen concentration can be smoothly controlled by controlling the rotation speed of the quartz crucible under AC power.

In particular, when controlling the rotational speed of the crucible using a silicon single crystal ingot growth apparatus having a heater using AC current, the oxygen concentration can be more smoothly adjusted in response to the requirements of the customer.

In addition, according to the oxygen concentration control method of the silicon single crystal ingot of the present invention, it is possible to grow high quality silicon single crystal ingot of high oxygen concentration with high productivity.

In addition, according to the oxygen concentration control method of the silicon single crystal ingot of the present invention, it is possible to grow a high quality silicon single crystal ingot of low oxygen concentration with high productivity.

In addition, according to the silicon single crystal ingot and wafer of the present invention, it is possible to produce silicon single crystal ingots and wafers of various concentrations of oxygen while maintaining high productivity.

In addition, according to the method for adjusting the oxygen concentration of the silicon single crystal ingot of the present invention, by controlling the crucible rotation speed using an ingot growth apparatus equipped with an AC heater, a silicon single crystal ingot and a wafer having a relatively large diameter and relatively low oxygen content can be provided. Can be.

In particular, by controlling the rotational speed of the quartz crucible under AC power to control the oxygen concentration of the silicon single crystal ingot, it is possible to manufacture silicon single crystal ingots and silicon wafers of various specifications of 8-17 ppma in response to customer demands.

In the present invention, when a silicon single crystal ingot growth apparatus using a silicon single crystal silicon ingot growth apparatus having a heater using an AC current is grown, a silicon single crystal using a silicon single crystal silicon ingot growth apparatus including a heater using a DC current is used. This is due to the fact that the oxygen concentration can be smoothly adjusted according to the change in the crucible rotation speed, rather than growing the ingot.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only intended to illustrate the invention, so the scope of the invention is not limited by these examples.

The oxygen concentration control method of the silicon single crystal ingot grown by the Czochralski method according to the embodiment of the present invention controls the oxygen concentration eluted from the crucible by controlling the rotational speed of the crucible containing the silicon melt. At this time, in order to adjust the oxygen concentration of the grown silicon unitary ingot to various specifications, it is preferable to use a silicon single crystal growth apparatus having a heater or AC graphite heating element using AC current.

1 is a cross-sectional view showing a process of growing a silicon single crystal ingot by the Czochralski method according to an embodiment of the present invention. As shown in FIG. 1, the apparatus for manufacturing a silicon single crystal ingot according to an embodiment of the present invention includes a chamber 10, and growth of the silicon single crystal ingot is performed in the chamber 10.

In the chamber 10, a quartz crucible 20 containing a silicon melt SM is installed, and a graphite crucible 25 made of graphite is installed outside the quartz crucible 20 to support the quartz crucible 20. do.

 The graphite crucible 25 is fixedly installed on the rotation shaft 30, which is rotated by a driving means (not shown) to raise the crucible 20 while rotating the quartz crucible 20 so that the solid-liquid interface has the same height. Keep it. The graphite crucible 25 is surrounded by the heater 40 at predetermined intervals, and the heater 40 is surrounded by the cylindrical heat insulating material 45, wherein the cylindrical heat insulating material 45 is heat dissipated from the heater 40. It is prevented from spreading toward the wall of the chamber 10 to improve the thermal efficiency.

The heater 40 is installed on the side of the graphite crucible 25 and basically serves to melt a high-purity polycrystalline silicon mass loaded in the quartz crucible 20 into a silicon melt SM. That is, until now, the heater mainly used a heater using a DC current, and in the role thereof, only the heat was generated to melt the polycrystalline silicon lump.

However, in the present invention, when using a silicon single crystal ingot growth apparatus using AC current, it was found that the oxygen concentration of the silicon single crystal ingot is sensitively changed according to the crucible rotation speed.

2 is a graph showing the results of measuring the oxygen concentration change according to the change in the rotation rate of the quartz crucible in the AC power source for each length of the silicon single crystal ingot according to an embodiment of the present invention. That is, in a silicon single crystal growth apparatus having a heater using an AC current, a silicon single crystal ingot is grown while continuously changing the rotation speed of the crucible containing the silicon melt, and the silicon single crystal ingot grown while the rotation speed is changed. The oxygen concentration in the glass was continuously measured and plotted against the length of the silicon single crystal ingot. Referring to FIG. 2, the oxygen concentration tends to decrease as the crucible rotation speed decreases, but when the crucible rotation speed is lower than 1.2 rpm, the oxygen concentration tends to increase as the crucible rotation speed decreases. It can be seen that.

As shown in Figure 2, the method of controlling the oxygen concentration of the silicon single crystal ingot by adjusting the rotational speed of the quartz crucible under the AC power source according to an embodiment of the present invention, in response to the various oxygen concentration requirements of the customer, in particular less than 17ppma It is very useful for producing silicon single crystal ingots and silicon wafers in the oxygen concentration range.

In the case of growing an ingot using the AC heater 40 according to an embodiment of the present invention, a magnetic field is generated as a frequency is generated by an alternating current, and the magnetic field controls the convection of the melt to increase the oxygen concentration in the ingot. It can be adjusted more easily. At this time, the periodic fluctuation of the magnetic field due to the alternating current serves to promote oxygen dissolution at the surface of the quartz crucible by reducing the oxygen dissolution at the interface between the quartz crucible and the silicon melt and the thickness of the diffusion boundary layer.

In other words, when the silicon single crystal ingot is grown while controlling the rotational speed of the quartz crucible using the AC heater, the silicon single crystal ingot can be easily varied by controlling the oxygen elution from the quartz crucible and the oxygen migration path in the silicon melt. Can grow.

In particular, when the crucible rotation rate is adjusted to about 0.3 to 0.5 to produce high quality silicon single crystal ingots, not only the diffusion boundary is reduced by vibration but also the reaction rate is increased to increase oxygen from the quartz crucible. Elution is easily controlled.

By adjusting the rotation speed of the quartz crucible as described above, it is possible to grow a high quality silicon single crystal ingot having a high oxygen concentration at a rapid growth rate, so that the productivity can be improved by about 20 to 30%.

In order to grow the silicon single crystal ingot at low oxygen concentration, the crucible rotation speed is preferably controlled at 0.8 rpm or more and 1.5 rpm or less, and in order to grow at high oxygen concentration, the crucible rotation speed is 0.1 rpm or more and 0.7 rpm or less. It is desirable to be controlled.

The amount of the eluted oxygen is preferably controlled so that the oxygen concentration in the silicon single crystal ingot is 12 ppm or more and 17 ppm or less. In addition, the amount of the eluted oxygen is preferably controlled so that the oxygen concentration in the silicon single crystal ingot is 8 ppm or more and less than 12 ppm.

Example 1

Using a silicon single crystal ingot growth apparatus with an AC heater of FIG. 1, a single crystal silicon ingot (150 mm in diameter) was pulled from a crucible having a diameter of 460 mm having 50 kg of polycrystalline silicon. At this time, the rotation speed of the crystal was in the range of 18-22 rpm, the crucible rotation speed was fixed at 0.3 rpm.

In Fig. 3, the oxygen concentration when the quartz crucible is rotated at 0.3 rpm in an AC power source is shown as a graph of the length of the silicon single crystal ingot. As shown in Fig. 3, the oxygen concentration of the silicon single crystal ingot pulled up under the above conditions is 14-17 ppma.

Example 2

A single crystal silicon ingot was pulled up in the same manner as in Example 1 except that the crucible rotation speed was fixed at 0.5 rpm.

3 shows the oxygen concentration when the quartz crucible rotation speed was fixed at 0.5 rpm. As shown in Fig. 3, the oxygen concentration of the silicon single crystal ingot pulled up under the above conditions is 12-15 ppma.

Example 3

A single crystal silicon ingot was pulled up in the same manner as in Example 1 except that the crucible rotation speed was fixed at 1.1 rpm.

3 shows oxygen concentration when the quartz crucible rotation speed was fixed at 0.5 rpm. As shown in Fig. 3, the oxygen concentration of the silicon single crystal ingot pulled up under the above conditions is 8-12 ppma.

1 is a schematic cross-sectional view of a typical silicon single crystal ingot growth apparatus,

2 is a graph showing the change in oxygen concentration with respect to the length of the silicon single crystal ingot according to the quartz crucible rotation speed change in the AC power source according to an embodiment of the present invention,

3 is a graph showing the oxygen concentration when the quartz crucible rotation speed is fixed at 0.3 rpm, 0.5 rpm, and 1.1 rpm in the AC power source according to the embodiment of the present invention with respect to the length of the silicon single crystal ingot.

<Code Description of Main Parts of Drawing>

10 chamber 20 quartz crucible

25: graphite crucible 30: rotating shaft

40; AC heater 45: cylindrical insulation

Claims (7)

In the oxygen concentration control method of silicon single crystal ingot grown by Czochralski method, A method for adjusting the oxygen concentration of a silicon single crystal, characterized by controlling the oxygen concentration eluted from the crucible by controlling the rotational speed of the crucible containing the silicon melt of the silicon single crystal ingot growth apparatus with a heater using AC current. The method of claim 1, The eluted oxygen amount is controlled so that the oxygen concentration in the silicon single crystal ingot is 12ppma or more and 17ppma or less. The method of claim 1, The eluted oxygen amount is controlled so that the oxygen concentration in the silicon single crystal ingot is controlled to be 8ppma or more and less than 12ppma. The method of claim 1, Rotational speed of the crucible is controlled to the oxygen concentration of the silicon single crystal, characterized in that controlled to more than 0.8 rpm to 1.5 rpm. The method of claim 1, Rotational speed of the crucible is controlled to the oxygen concentration of the silicon single crystal, characterized in that controlled to 0.1 rpm or more and 0.7 rpm or less. In silicon single crystal ingot grown by Czochralski method, A silicon single crystal ingot having an oxygen concentration of 9 ppm or more and 15 ppm or less in a silicon single crystal ingot grown by controlling the rotation speed of a crucible containing a silicon melt of a silicon single crystal ingot growth apparatus having a heater using AC current. In the apparatus for growing a silicon single crystal by the Czochralski method, chamber; A crucible installed inside the chamber and containing a silicon melt; A heater installed on the side of the crucible to heat the silicon melt and using AC current; And And a pulling mechanism for pulling up the silicon single crystal grown from the silicon melt.

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