JP2572051B2 - Silicon wafer for epitaxial growth and method of manufacturing the same - Google Patents

Description

The present invention relates to a silicon wafer, particularly to a silicon wafer for epitaxial growth and a method for manufacturing the same.

[Prior Art] With the enhancement of performance of bipolar elements and MOS elements including power elements, the range of use of silicon wafers for epitaxial growth has been expanded, and reduction of crystal defects in silicon wafers has been strongly demanded. . On the other hand, the development of silicon wafer manufacturing technology is also progressing, and for the generation of crystal defects due to contamination,
We are addressing issues such as cleaning the manufacturing environment, automating wafer handling equipment, and purifying the chemicals used. Are being addressed by improvements. However, none of these measures are sufficient and satisfactory.

To compensate for the above imperfections, it is necessary to control the concentration of oxygen mixed into the silicon wafer. For that purpose, the amount of oxygen mixed into the single crystal from the quartz crucible used in the single crystal pulling apparatus is strictly controlled, and the silicon wafer generated during the additional heat treatment before the epitaxial growth step and during the heat treatment during the epitaxial growth step Intrinsic gettering or internal wafer gettering (hereinafter referred to as IG)
EG) or extrinsic gettering or wafer backside gettering (hereinafter referred to as EG), or a combination thereof.

Here, IG refers to the local fixation of impurities related to the amount of saturated nuclei in the silicon wafer determined by the heating temperature of the silicon wafer and the amount of precipitation nuclei determined by the heat history after crystallization. . EG refers to mechanical damage, fine silicon polycrystal or fine Si ₃ N, which is performed while controlling the other surface (hereinafter referred to as “back surface”) of one side of the silicon wafer on which epitaxial growth is performed, while controlling the other surface.
₄ Refers to the local fixation of impurities by polycrystal or the like.

[Problems to be solved by the present invention] The gettering property of IG is not good for a silicon wafer having a small amount of precipitated oxygen. However, if the amount of oxygen is excessively increased for the purpose of increasing the gettering property of the IG, there is a problem that a slip or the like due to a precipitate occurs at the time of the wafer heat treatment, so that the oxygen concentration is 10 × 10 ¹⁷ at.
IG is not applicable to silicon wafers of about oms / cm ³ (oxygen content according to the measurement standard given by the 1981 edition of ASTM), so EG is used for such silicon wafers. ing.

However, for example, in EG such as the backside mechanical damage method, a fine powder such as SiO ₂ , SiC, Al ₂ O ₃ is mixed into a high-speed air stream or a high-speed water stream, and these are sprayed on the back side of the silicon wafer, or Since the back surface of the silicon wafer is rubbed with a brush made of an organic material mixed with fine powder, it is extremely difficult to maintain the cleanliness of the back surface of the silicon wafer.

[Means for Solving the Problems] An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a silicon wafer for epitaxial growth having an IG effect even at a low oxygen concentration. .

An object of the present invention is to provide a silicon wafer for epitaxial growth, wherein a silicon wafer previously containing an impurity for doping is irradiated with 1 × 10 ¹² atoms / cm ² or more of fast neutrons so as to have an impurity trapping effect. Achieved by wafer.

In addition, the object is to provide a silicon wafer previously containing an impurity for doping with a reactor having a thermal neutron / fast neutron ratio of 30 or less to provide 1 × 10 ¹² / cm ² or more fast neutrons in order to have an impurity trapping effect. This is also achieved by a method for producing a silicon wafer for epitaxial growth, characterized by irradiation.

[Action] The oxygen concentration is about 0.5 × 10 ¹⁷ atoms / cm ³ or more and 1 × 10
Heating a silicon wafer irradiated with fast neutrons of ¹⁶ / cm ² or more to 900 ° C, the wavelength of this silicon wafer
The infrared absorption of 1.1 to 2 μm increases. This phenomenon is considered to be due to scattering of a particle region having a diameter substantially equal to the wavelength of the incident infrared light and having a very large number of minute angle shifts. This means that, according to the above-mentioned electron microscopic observation of the silicon wafer, 1 × 10 ³ particles / cm ³ or more of particle regions having a small angle deviation of about 0.1 ° or less of about 0.1 to 10 μm are generated, and It is clear from the fact that slight distortion is confirmed at the boundary of the particle region. By the way,
This particle region has a gettering effect,
According to the above-mentioned observation, it is confirmed that the gettering ability disappears after about one hour or more.
Unlike the slip and large precipitation that hinder the device characteristics, the gettering effect against impurities, surface processing damage, and the like can be improved in the early stage of the device manufacturing process that strongly influences the device characteristics.

Example In order to confirm the above-mentioned phenomenon, the effect of irradiating silicon wafers manufactured from the same rod with 5 × 10 ¹⁶ high-speed neutrons / cm ² or more was measured. Shown in the figure.

 Notes 1) to 4) in FIG. 1 are as follows.

Note 1) The fast neutron irradiation dose is approximately 5 × 10 ¹⁶ / cm ² .

2) The value converted by the infrared absorption measurement method according to the 1981 edition ASTM standard.

3) In process A, epitaxial growth is performed by SiCl ₃ H on a silicon wafer that has been subjected to heat treatment at 900 ° C. for 10 minutes after irradiation with high-speed neutrons, and in process B, the silicon wafer subjected to process A is slightly contaminated with Fe. Done.

4) NTD indicates a silicon wafer that has been subjected to neutral irradiation conversion doping.

In FIG. 1, all of the silicon wafers Nos. 1 to 32 are manufactured from a silicon single crystal pulled under a transverse magnetic field.

From this result, it is understood that the silicon wafer irradiated with fast neutrons has good gettering property by IG. By the way, when the irradiation amount of fast neutrons is 5 × 10 ¹⁶ / cm ² or more, depending on the oxygen concentration difference of silicon wafer, IG
No difference in gettering property was observed, and the difference in the resistance of the silicon wafer was also in the range of 5 to 20 Ωcm for the B and As dopants, and 30 to 50 Ωcm for the P dopant.
There is no difference in gettering property by IG in the range of.

FIG. 2 focuses on the work-induced stacking faults, that is, whether or not the work-induced defects appear on the epitaxial growth surface after undergoing the epitaxial growth step, and when they do occur, the amount of occurrence is used as a criterion for determining the quality of the B20 Ωcm-doped Si. And P
Fast neutron irradiation dose of 1 × 10 ¹⁴ / cm ^{2 for} 50ΩcmNTDSi
6 is a graph showing data obtained by measuring the number of processing-induced stacking faults by a line 1 while changing the number of processing-induced stacking faults in six ways between 間 の 1 × 10 ¹⁷ / cm ² . In FIG. 2, the average value (7 × 10 ³ / cm ² ) without irradiation with fast neutrons is indicated by a broken line 2,
The upper limit of measurement data at each fast neutron dose is
If it extended as a dashed line 3 in the drawing, a chain line this one point because it substantially passes through the point of the fast neutron irradiation amount 1 × 10 ¹² pieces / strain-induced defect number 10 ⁴ in cm ² / cm ^2, fast neutron irradiation When the amount is 1 × 10 ¹² / cm ² or more, it is considered that the number of processing-induced defects can be reduced as compared with the case where high-speed neutron irradiation is not performed, and therefore, the gettering property by IG can be improved.

Here, the above-mentioned fast neutron irradiation dose of 1 × 10 ¹⁴ particles / cm ² ~
Six variations between 1 × 10 ¹⁷ / cm ² used the reactors shown in Table 2.

Incidentally, as is clear from Table 1, the thermal neutron / fast neutron ratio of the reactor used for fast neutron irradiation is about 6 to 3000.
And the flux density of fast neutrons is in the range of about 2 × 10 ⁹ / cm ² · s to 1 × 10 ¹³ / cm ² · s. Therefore, for example, the time required for fast neutron irradiation at 1 × 10 ¹⁴ / cm ² is 10 seconds to 14 hours, and the time required for fast neutron irradiation at 1 × 10 ¹⁶ / cm ² is 17 minutes to 1389. Time. That is, if a proper reactor is selected according to the required fast neutron irradiation dose, the required fast neutron irradiation dose can be irradiated with a sufficiently short time and high accuracy.

When irradiating fast neutrons, it must be noted that thermal neutrons are also irradiated simultaneously with fast neutrons. With this thermal neutron irradiation, since Si ³⁰ is converted to P ³¹ , the P generated in B-doped Si is
Compensation of the B doubant occurs due to the increase in resistance, and in As-doped Si, the resistance decreases due to P generated. These changes are smaller as the resistance of the original Si is lower, and when the resistance is 10 Ωcm or less, the above-mentioned change is not more than 10 even with the fast neutron irradiation by any of the aforementioned reactors.
% Or less. If the original resistance is more than 10 Ωcm, the compensation corresponding to the thermal neutron dose is required.

In order to reduce the amount of compensation due to this fast neutron irradiation and to increase the effect of fast neutron irradiation, it is sufficient to use a reactor with a small thermal neutron / fast neutron ratio. The irradiation time can be shortened, which is advantageous from the viewpoint of improving productivity. From the above experiments, it is preferable that the thermal neutron / fast neutron ratio is 30 or less.

According to experiments, no difference was found between the heat-treated silicon wafer and the non-heat-treated silicon wafer regarding the usefulness of the heat treatment before the epitaxial growth step for the silicon wafer manufactured by the method of the present invention. The reason is that there is a limit in shortening the time from the start of heating the silicon wafer into the epitaxial growth furnace to the start of the epitaxial growth process. This is because it will occur. Therefore, in practice, there is no problem even if the heat treatment before the epitaxial growth step is omitted, high-speed neutron irradiation is performed, and the wafer is machined and immediately turned into the epitaxial growth step.

[Effects of the present invention] According to the silicon wafer of the present invention, the number of process-induced defects in the silicon wafer can be reduced as compared with the case where high-speed neutron irradiation is not performed, so that the gettering property by IG can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing the effect when a silicon substrate is irradiated with fast neutrons, and FIG. 2 is a graph showing the effect of the method of the present invention. 1 ... measurement data, 2 ... mean value without fast neutron irradiation 3 .... extension line of measurement data upper limit.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Eiichi Taji 30 Soya, Hadano City, Central Research Laboratory of Toshiba Ceramics Co., Ltd. (56) References JP-A-54-77063 (JP, A)

Claims (5)

(57) [Claims] 1. A silicon wafer for epitaxial growth, wherein a silicon wafer previously containing an impurity for doping is irradiated with 1 × 10 ¹² / cm ² or more of high-speed neutrons in order to have an impurity trapping effect. 2. The silicon wafer having an oxygen concentration of 5 × 10
^2. The silicon wafer according to claim 1, wherein the silicon wafer has a density of ¹⁶ atoms / cm ³ or more. 3. The silicon wafer according to claim 1, wherein the doping impurity is boron, arsenic, or phosphorus. 4. The silicon wafer according to claim 3, wherein the phosphorus is obtained by neutron irradiation conversion doping. 5. A thermal neutron / silicon wafer containing a doping impurity in advance so as to have an impurity trapping effect.
Reactor with fast neutron ratio of 30 or less produces 1 fast neutron
A method for producing a silicon wafer for epitaxial growth, characterized by irradiating at least × 10 ¹² / cm ² .