KR100589691B1 - A silicon wafer - Google Patents

Abstract

According to the present invention, a silicon wafer includes a first region in which a flow pattern defect (FPD) and a direct surface oxide defect (DSOD) coexist, a second region in which only a DSOD is present without FPD, and a third region including an oxidative lamination region And a fourth region in which at least one of the vacancy predominant defect free region and the interstitial predominant defect free region is formed. In addition, the silicon wafer according to the present invention has an initial oxygen concentration substantially equal to or less than 9.5 ppma (parts per million atoms, New ASTM) and has a carbon content of 1 × 10 ⁶ to 2.5 × 10 ¹⁶ pieces / cm ³ . Is added.

Monocrystalline, Silicon, Czochralski, Defective, Oxygen

Description

Silicon Wafers {A SILICON WAFER}

1 is a plan view showing an arrangement of regions having different defect characteristics in a silicon wafer according to the present invention.

2 is a view schematically showing a growth rate along the length of a single crystal silicon ingot when growing a silicon single crystal by using the Czochralski method to manufacture a silicon wafer according to the present invention.

3 is a diagram illustrating an example of a heat treatment cycle that may exhibit a difference in oxygen precipitation tendency in each region of a silicon wafer.

FIG. 4 is an image of a minority carrier life time (MLCT) scan after the heat treatment according to FIG. 3 is performed on the silicon wafer according to Example 1. FIG.

5 is a diagram illustrating an example of a heat treatment cycle capable of detecting oxidative lamination defects of a silicon wafer.

FIG. 6 is a view illustrating mapping an oxidative stacked defect after performing a heat treatment according to FIG. 5 on a silicon wafer according to Example 1. FIG.

7 is a diagram illustrating a DSOD after performing a predetermined heat treatment on the silicon wafer according to Example 1. FIG.

FIG. 8A shows the result of a gate oxide integrity (GOI) evaluation of a silicon wafer according to Example 1. FIG.

8B illustrates a GOI evaluation result of a silicon wafer according to a comparative example.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon wafer, and more particularly, to a silicon wafer capable of improving oxide film breakdown voltage characteristics while reducing oxygen concentration in the silicon wafer.

Recently, with the development of the information technology (IT) industry, interest in semiconductors, which are the core technologies of the information technology industry, is increasing. In addition, such semiconductors can be applied to various fields such as computers, home appliances, mobile phones, liquid crystal displays, and the like, and research on such semiconductor technologies is being actively conducted.

In order to manufacture a semiconductor, a process of manufacturing a wafer, injecting predetermined ions into the wafer, and forming a circuit pattern is required. In this case, in order to manufacture a wafer, single crystal silicon must first be grown in an ingot form, and for this, a Czochralski (CZ) method or a floating zone (FZ) method may be applied. However, in the case of growing single crystal silicon by applying the floating zone method, it is common to grow single crystal silicon by applying the Czochralski method, which is difficult to manufacture large diameter silicon single crystal and has a very high process cost.

The Czochralski method is a method of growing a silicon single crystal by melting silicon in a quartz crucible, immersing a seed crystal of single crystal silicon in molten silicon, and then pulling it while rotating at a predetermined speed. The single crystal silicon ingot manufactured by the Czochralski method is sliced, and lapping, etching, cleaning and polishing are performed to complete the manufacture of the silicon wafer.

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. In addition, high temperature heat treatment is necessary during the ion implantation process during the semiconductor manufacturing process. In this case, a high concentration of oxygen is required to prevent deformation of the silicon wafer, but as the development of technology enables the low temperature heat treatment, a high oxygen concentration is required. It was reduced. The reason is that the oxygen present in the silicon wafer later causes coarse oxygen deposition defects (eg, oxide induced stacking faults (OiSF)), which can also act as a leakage source, adversely affecting semiconductor device operation. This can be a further problem as semiconductors become highly integrated and technologies to control metal contamination are developed.

 In order to solve this problem, research is being conducted to remove the oxidative lamination region in which a potential nucleus that can grow by coarse oxygen precipitation defects is present. As such a method, there is a method of pulling out the oxidized lamination defect out of the silicon wafer surface or shrinking the oxidized lamination defect region as in the invention described in Japanese Patent Laid-Open No. 1990-267195. However, the method of extracting oxidative lamination defects out of the silicon wafer surface has a problem of decreasing yield by increasing large vacancy defects, and the method of shrinking oxidative lamination defect regions has to decrease the growth rate of single crystal silicon to increase productivity. There is a problem of lowering.

Another method to prevent problems caused by coarse oxygen precipitation is to lower the initial oxygen concentration of the silicon wafer. However, when reducing the initial oxygen concentration of the silicon wafer, intrinsic crab that removes metal impurities There is a problem that the turing ability is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a silicon wafer capable of suppressing precipitation of coarse oxygen precipitation defects even in the presence of oxidatively stacked defect regions and having excellent intrinsic gettering capability. It is.

According to the present invention, a silicon wafer includes a first region in which a flow pattern defect (FPD) and a direct surface oxide defect (DSOD) coexist, a second region in which only a DSOD is present without FPD, and a third region including an oxidative lamination region And a fourth region in which at least one of the vacancy predominant defect free region and the interstitial predominant defect free region is formed. In addition, the silicon wafer according to the present invention has a carbon value of 1 × 10 ⁶ to 2.5 × 10 ¹⁶ pieces / cm ^{3 having} an initial oxygen concentration substantially equal to or less than 9.5 ppma (parts per million atoms, New ASTM). Is added.

At this time, the initial oxygen concentration is preferably in the range of 4.5 to 9.5 ppma. In addition, a bulk micro defect (BMD) density of the silicon wafer may have a value equal to or greater than 1 × 10 ⁶ holes / cm ² .

The first region, the second region, the third region, and the fourth region may be formed in order from the center of the silicon wafer toward the edge.

The silicon wafer may be grown and manufactured by the Czochralski method.

Hereinafter, referring to the accompanying drawings, a silicon wafer according to the present invention will be described in detail.

1 is a plan view showing an arrangement of regions having different defect characteristics in a silicon wafer according to the present invention.

Referring to FIG. 1, a silicon wafer according to the present invention includes a first region 10, a second region 20, a third region 30, and a fourth region 40. At this time, each of the first region 10, the second region 20, the third region 30, and the fourth region 40 has different defect characteristics. In the following, the terms indicating the type of defects are named according to a method for finding defects which may provide a cause of failure in an electronic circuit to be formed on a silicon wafer by a subsequent process.

In the drawing, for example, the first region 10, the second region 20, the third region 30, and the fourth region 40 are sequentially formed from the center of the silicon wafer toward the edges. The invention is not limited to this, and it is sufficient if the regions coexist in the silicon wafer, and the arrangement state thereof may be different, which is also within the scope of the present invention.

The first region 10 is located at the center of the silicon wafer and may be formed by coexistence of a flow pattern defect (FPD) and a direct surface oxide defect (DSOD). FPD is a kind of defect in vacancy and has a coarse size. On the other hand, DSOD is a vacancy defect having a fine size, and it is generally known that the wafer does not cause a big problem even in the wafer used in the manufacturing process of the highly integrated semiconductor device.

The second region 20 is a region capable of forming only DSDO, which is a kind of minute vacancy defects in a subsequent semiconductor process. Accordingly, the FPD, which is a kind of coarse vacancy defects, does not exist in the second region 20, and only fine vacancy defects exist, and defects that do not cause problems even when used for high-density semiconductor fabrication generally exist. Area. Therefore, the second wafer 20 can be widely distributed to form a silicon wafer capable of improving the yield of the semiconductor manufacturing process.

The third region 30 is generally formed of an oxidized stacked defect region and may also be referred to as an oxidation-induced stacking fault ring (OiSF ring). Unlike the central part of the silicon single crystal ingot, which solves the latent heat of coagulation through heat conduction between the silicon, the outer surface of the silicon ingot is directly in contact with the gas phase, and thus the latent heat of coagulation can be more easily resolved by heat radiation. The third region 30 is inevitably present at the outer circumference of the silicon ingot even when only the micro vacancy predominant defect is uniformly higher than the center of the silicon ingot.

The fourth region 40 may be a bacon predominant defect free region or a bacon predominant defect free region and an interstitial predominant defect free region.

As described above, the silicon wafer including the first region 10, the second region 20, the third region 30, and the fourth region 40 has a silicon single crystal while gradually decreasing the growth rate as shown in FIG. 2. It can be prepared by growing the ingot and slicing it.

On the other hand, the third region 30 is a defect-free region having a tendency that the vacancy concentration is less than or equal to the threshold, similarly to the vacancy predominant defect-free region. However, when a general silicon wafer is applied to a semiconductor manufacturing process, coarse oxygen precipitation defects (eg, oxidation-induced stacking fault defects (OiSF)) are formed in the third region 30 by heat treatment. It is known.

In the present invention, the initial oxygen concentration of the silicon wafer is controlled to prevent the occurrence of such coarse oxygen precipitation defects. That is, in the present invention, coarse oxygen precipitation defects can be prevented even when an oxidatively stacked defect region inevitably generated when growing a silicon single crystal by the Czochralski method is widely present in the silicon wafer.

To this end, in the present invention, the initial oxygen concentration of the silicon wafer has a value substantially equal to or less than 9.5 ppma (parts per million atoms, New ASTM). Based on the results of this study, when the initial oxygen concentration is 9.5 ppma or less, coarse oxygen precipitation defects are not formed even after the heat treatment in a predetermined semiconductor manufacturing process, but when the initial oxygen concentration exceeds 9.5 ppma, Since coarse oxygen precipitation defects may be formed by subsequent heat treatment, the initial oxygen concentration is limited to 9.5 ppma or less in the present invention.

In addition, since silicon has an oxygen solubility of approximately 4 ppma at 1000 ° C., the initial oxygen concentration of the silicon wafer should be at least greater than this. If the initial oxygen concentration is less than 4 ppma, bulk micro defects (BMD) that getter metal impurities cannot be formed to have sufficient density. At this time, in order to ensure the delta oxygen concentration at least 0.5 ppma or more, the initial oxygen concentration is required to have a value of 4.5 ppma or more. Here, the delta oxygen concentration refers to the difference between the initial oxygen concentration and the final oxygen concentration measured after performing a predetermined heat treatment on the silicon wafer.

In the silicon wafer according to the present invention, carbon is added. For this purpose, a predetermined concentration may be added to the silicon wafer by, for example, doping carbon, or optionally adding a proportion of carbon into the molten silicon. In the present invention, it can be applied to all known carbon addition techniques in addition to the above-described method, which also belongs to the scope of the present invention.

It is possible to improve the quality of the silicon wafer by adding a predetermined element to the silicon wafer. In this case, the added element may cause other problems. For example, in the case of the silicon single crystal grown by the Czochralski method, the effect of the point defect on the oxygen precipitation is as follows. In the case of nitrogen, the concentration of residual vacancy in the temperature range where oxygen precipitation nuclei are formed is reduced by lowering the coagulation start temperature of bacon sie Height plays a role. These high density bacones combine with nitrogen to form coarse oxygen precipitation defects, resulting in increased oxidative lamination defects.

In the present invention, a carbon atom capable of improving the gettering ability is added to the oxygen precipitation tendency without adversely affecting it. That is, the carbon atoms act as a nucleus of fine oxygen precipitation directly, without affecting defect behavior, that is, without changing the oxidative lamination region, thereby contributing to the formation of oxygen precipitates in the bulk of the silicon wafer. . This oxygen precipitate serves as a gettering site for removing metal impurities in the silicon wafer bulk. That is, by adding carbon, sufficient BMD concentration can be realized in the silicon wafer bulk.

At this time, carbon is preferably added at a concentration of 1 × 10 ⁶ to 2.5 × 10 ¹⁶ pieces / cm ³ in consideration of the allowable range for application to the semiconductor manufacturing process while promoting the generation of oxygen precipitates. At this time, the bulk micro defect (BMD) density of the silicon wafer according to the present invention may have a value equal to or greater than 1 × 10 ⁶ holes / cm ² .

That is, the present invention suggests an appropriate range of the initial oxygen concentration and the carbon concentration present in the silicon wafer, thereby acting as a BMD in the bulk of the wafer while preventing generation of coarse oxygen precipitation defects that may be a problem in quality characteristics. Can increase oxygen precipitates.

In addition, the silicon wafer according to the present invention has a high oxide withstand voltage characteristic can be used as a substrate of the power semiconductor device. At this time, the high oxide withstand voltage characteristic refers to the strength of the gate voltage that the oxide film formed on the wafer can withstand while performing the function of the gate insulating film without dielectric breakdown. Such wafer oxide withstand voltage characteristics are usually determined by GOI (gate oxide integrity) evaluation. Can be confirmed. GOI evaluation may indirectly confirm a fail rate of the semiconductor device.

Hereinafter, the present invention will be described in more detail through experimental examples. These experimental examples are for illustrating the present invention and the present invention is not limited thereto.

In the following experimental example, Example 1 having an initial oxygen concentration of 9.5 ppma and a carbon concentration of 1 × 10 ¹⁶ atoms / cm ³ , Example 2 having an initial oxygen concentration of 8.5 ppma and carbon atoms of 1 × 10 ¹⁶ atoms / cm ³ , And the initial oxygen concentration was 10.5 ppma and the experiment was conducted for a comparative example without adding carbon.

Experimental Example 1

Using the Czochralski method to grow a single crystal silicon ingot while reducing the growth rate as shown in FIG. 2, the silicon wafer of Example 1 was prepared by slicing it and doping with carbon. The silicon wafer according to Example 1 was subjected to a heat treatment (see FIG. 3) to see a difference in oxygen precipitation tendencies in regions having different defects. In other words, the silicon wafer was maintained at 800 ° C. for 4 hours in an N ₂ atmosphere, and then heated to 1000 ° C. for 16 hours after the temperature was increased.

After performing the heat treatment, the silicon wafer according to Example 1 was stripped from hydrofluoric acid (HF) solution, followed by MCLT (minority carrier life time) scanning, and the results of the MCLT are shown in FIG. 4.

As shown in FIG. 4, it can be seen that the wafer according to the present invention has an even distribution of oxygen precipitates even in regions having different defects because oxygen precipitates are evenly distributed over the entire region. That is, the wafer according to the present invention has an even deposition tendency of oxygen can produce a semiconductor device of excellent quality when manufacturing a semiconductor device using such a wafer.

Experimental Example 2

Using the Czochralski method, single crystal silicon ingots were grown while decreasing the growth rate as shown in FIG. 2, and then sliced and doped with carbon to prepare silicon wafers according to Examples 1 and 2. The silicon wafer was subjected to a heat treatment (see FIG. 5) to detect coarse oxygen lamination defects in regions having different defects. That is, after maintaining a temperature lower than 1000 ° C. for a predetermined time in a mixed gas atmosphere of oxygen gas (O ₂₎ and hydrogen gas (H ₂₎ , the temperature is raised to 1000 ° C. and maintained at 1000 ° C. for 3 hours. The temperature was raised to 1150 ° C. and then maintained at 1150 ° C. for 110 minutes, followed by a heat treatment to lower the temperature to 800 ° C. The above heat treatment was also performed on the silicon wafer according to the comparative example.

Table 1 shows the coarse oxygen precipitation defect concentrations in the silicon wafers according to Examples 1, 2, and 3.

Then, each part of the silicon ingot for manufacturing Examples 1 and 2 was sliced and mapped coarse oxygen precipitation defects visually using intensity light. In this case, the result of mapping the silicon wafer sliced in the silicon ingot for manufacturing Example 1 is shown in Figure 6, the DSOD measurement of the sliced silicon wafer in the P portion of Figure 6 and the result is shown in Figure 7 It was.

Initial Oxygen Concentration [ppma] Carbon concentration [pcs / cm ³ ] Coarse Oxygen Defect Concentration [pieces / cm ² ] Example 1 9.5 1 × 10 ¹⁶  0.8 Example 2 8.5 1 × 10 ¹⁶ 0 Comparative example      9.5    - 45

As shown in Table 1, the concentration of coarse oxygen precipitation defects was very low in the silicon wafers according to Examples 1 and 2, whereas the concentration of coarse oxygen precipitation defects was very high in the silicon wafer according to the comparative example. have.

6, it can be seen that a silicon wafer satisfying the conditions of Example 1 is not found to have coarse oxygen precipitation defects in the oxidative lamination region even after a heat treatment capable of detecting oxidative lamination defects. In addition, referring to FIG. 7, it can be seen that the oxidized lamination defect region of the silicon wafer according to Example 1 has a very excellent characteristic in which even a DSOD, which is a microscopic defect that does not cause a significant problem in semiconductor operation, is not found.

These results were found to be the same in the silicon wafer according to Example 2. In other words, even in the silicon wafer having an initial oxygen concentration of 8.5 mmpa, coarse oxygen deposition defects were not detected and no DSOD was detected.

That is, since the silicon wafers according to Examples 1 and 2 have an appropriate initial oxygen concentration such that they do not form coarse oxygen precipitation defects, coarse oxygen precipitation defects are not formed even in the oxidatively stacked defect region. It is possible to manufacture a semiconductor device having excellent quality even with a high yield even if a semiconductor device is manufactured using a silicon wafer having a wide region of oxidative lamination defects inevitably present in a silicon wafer grown and manufactured by the Czochralski method. It means that there is.

Experimental Example 3

GOI evaluation was performed on silicon wafers according to Example 1 and Comparative Examples, and the results are shown in FIGS. 8A and 8B. In the GOI evaluation, the strength of the breakdown voltage (BV) at which the wafer was no longer tolerable and broken was measured at 218 points per wafer. According to the measured threshold voltage intensity, the failure is divided into A mode, B mode, and C mode, and is shown in a different color for each mode.

Referring to FIG. 8A, in the silicon wafer according to Example 1, current leakage does not occur even in an oxidized lamination region and no serious defects such as A mode or B mode are seen. On the other hand, referring to Figure 8b, it can be seen that in the silicon wafer according to the comparative example, a current leak occurs in the oxidized lamination defect region, causing serious defects such as A mode or B mode.

That is, the silicon wafer according to the present invention is excellent in the oxide pressure resistance characteristic, it is possible to effectively reduce the failure rate of the semiconductor device using such a silicon wafer.

Experimental Example 4

The BMD densities of the silicon wafers according to Examples 1, 2 and Comparative Examples were measured after the heat treatment shown in FIG. 3, and the results are shown in Table 2.

Initial Oxygen Concentration [ppma] Carbon concentration [pcs / cm ³ ] BMD density [pcs / cm ² ] Example 1 9.5 10 ¹⁶ 10 ⁶ Example 2 8.5 10 ¹⁶ 10 ⁶ Comparative example      9.5    - 10 ⁴

As shown in Table 2, it can be seen that the BMD densities of the silicon wafers according to Example 1 and Example 2 are significantly superior to the BMD densities of the silicon wafers according to the comparative example. That is, in the present invention, it can be seen that by adding carbon which can act as a nucleus for oxygen deposition, the gettering ability to remove metal impurities and the like can be improved by improving the BMD density in the bulk of the silicon wafer.

Although the present invention has been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims, the detailed description of the invention, and the accompanying drawings. It is natural to belong.

As described above, according to the silicon wafer according to the present invention, even when the oxidative lamination defect region is formed by having an appropriate initial oxygen concentration, coarse oxygen precipitation defects such as oxidative lamination defects do not occur, thereby causing such coarse oxygen precipitation defects. The problem which may arise by this can be prevented. That is, when manufacturing a semiconductor device using the silicon wafer according to the present invention it is possible to improve the yield of such a semiconductor device.

In addition, the addition of carbon at an appropriate concentration can increase the BMD density without adversely affecting the properties of defects, thereby improving the gettering ability of the wafer. In addition, the silicon wafer according to the present invention has excellent oxide breakdown voltage characteristics, and thus, a semiconductor device having such a silicon wafer and having a low defect rate can be manufactured.

Claims (5)

A first region in which a flow pattern defect (FPD) and a direct surface oxide defect (DSOD) coexist, a second region in which only the DSOD is present without FPD, a third region including an oxidative lamination region, and vacancy A fourth region in which at least one of the dominant defect region and the interstitial dominant defect region is formed is formed, A silicon wafer to which 1 × 10 ⁶ to 2.5 × 10 ¹⁶ pieces / cm ³ of carbon is added with an initial oxygen concentration having a value substantially equal to or less than 9.5 ppma (parts per million atoms, New ASTM). The method of claim 1, Silicon wafer in which the initial oxygen concentration is in the range of 4.5 to 9.5 ppma. The method of claim 1, A silicon wafer having a bulk micro defect (BMD) density of the silicon wafer equal to or greater than 1 × 10 ⁶ holes / cm ² . The method of claim 1, And the first region, the second region, the third region, and the fourth region are formed in order from the center of the silicon wafer toward the edge. The method of claim 1, The silicon wafer is grown by the Czochralski method (silicon wafer) manufactured.

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