METHOD FOR EVALUATING ATOMIC VACANCY IN SURFACE LAYER OF SILICON WAFER AND APPARATUS FOR EVALUATING THE SAME

• US 20160258908A1
• Filed: 11/05/2014
• Published: 09/08/2016
• Est. Priority Date: 11/08/2013
• Status: Abandoned Application

• Current Assignee: Niigata University
• Original Assignee: Niigata University
• Inventors: GOTO, Terutaka, NEMOTO, Yuichi, KANETA, Hiroshi, AKATSU, Mitsuhiro, MITSUMOTO, Keisuke
• Application Number:
  US15/031,187
• Publication Number:
  US 20160258908A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01N 2291/012 Phase angle
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force
• CPC Class Codes: G01N 2291/0423 Surface waves, e.g. Rayleigh waves, Love waves
• CPC Class Codes: G01N 2291/2697 Wafer or (micro)electronic parts
• CPC Class Codes: G01N 29/075 by measuring or comparing phase angle measuring frequencies or phase angles per se G01R23/00, G01R25/00
• CPC Class Codes: G01N 29/2437 Piezoelectric probes
• CPC Class Codes: G01N 29/2462 Probes with waveguides, e.g. SAW devices
• CPC Class Codes: H01L 22/12 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 electrical measurement of diffusions H01L22/14

Abstract

A method for evaluating atomic vacancies in a silicon wafer surface layer includes: element formation in which a pair of comb-shaped electrodes are formed on the same surface of a silicon sample over piezoelectric thin films; detection during which the sample is cooled and an ultrasonic pulse generated from one electrode while an external magnetic field is applied, the ultrasonic pulse being propagated through the sample surface and received by the other electrode, and a phase difference being detected between the ultrasonic pulse generated by the one electrode and the ultrasonic pulse received by the other electrode; and evaluation during which the sample surface elastic constant is determined on the basis of the phase difference, and the atomic vacancies in the sample surface are evaluated on the basis of changes in the elastic constant according to temperature or changes in the elastic constant according to the magnetic field intensity.

Claims

1. A method for evaluating atomic vacancy in a surface layer of a silicon wafer, comprising the steps of:

forming a pair of surface acoustic wave (SAW) devices which are arranged opposite to one another on the same main surface of a silicon sample;

generating an ultrasonic wave pulse by one of the surface acoustic wave (SAW) devices and propagating the ultrasonic wave in a surface layer of the silicon sample while the silicon sample is cooled under a condition of an application of magnetic field, and receiving the propagated ultrasonic wave pulse at the other of the surface acoustic wave (SAW) devices, thereby measuring a difference in phase between the injected ultrasonic wave pulse and the propagated ultrasonic wave pulse; and

calculating an elastic constant C_s of the surface layer of the silicon sample based on the difference in phase and evaluating a concentration “

N”

of atomic vacancy of the surface layer of the silicon sample based on a change of the elastic constant C_s with a temperature or a change of the elastic constant C_s with an intensity of the magnetic field.

2. The evaluating method as set forth in claim 1,

wherein the silicon sample is cooled within a temperature range of 10 mK to 20 K.

3. The evaluating method as set forth in claim 1,

wherein an intensity of the magnetic field is set within a range of 0 to 10 teslas.

4. The evaluating method as set forth in claim 1,

wherein each of the surface acoustic wave (SAW) devices comprises a piezoelectric film formed on the main surface of the silicon sample and a comb-shaped electrode formed on the piezoelectric film.

5. The evaluating method as set forth in claim 4,

wherein the piezoelectric film is made of zinc oxide (ZnO), aluminum nitride or polyvinylidene fluoride and the comb-shaped electrode is made of aluminum (Al) or copper (Cu).

6. The evaluating method as set forth in claim 1,

wherein the silicon sample is attached to a silver plate or a silver film.

7. The evaluating method as set forth in claim 1,

wherein the concentration “

N”

of atomic vacancy is defined by obtaining a low temperature softening Δ

C_s/C_s of the constant Cs of the surface layer of the silicon sample and considering that the softening of the elastic constant C_s of the surface acoustic wave (SAW) corresponds to the concentration of atomic vacancy of N=(1.6±

0.2)×

10¹²/cm³ as the use of unit of Δ

C_s/C_s=10<sup>−

4</sup>.

8. The evaluating method as set forth in claim 1,

wherein the concentration “

N”

of atomic vacancy is defined by obtaining a low temperature softening Δ

C_s/C_s dependent on a change of the intensity of the magnetic field within a range of 0 to 10 teslas when the elastic constant C_s of the surface layer of the silicon sample is calculated at a temperature within a range 10 mK to 50 mK and considering that the softening of the elastic constant C_s of the surface acoustic wave (SAW) corresponds to the concentration of atomic vacancy of N=(1.6±

0.2)×

10¹²/cm³ as the use of unit of Δ

C_s/C_s=10<sup>−

4</sup>.

12. A silicon wafer, comprising a concentration of atomic vacancy in a surface layer thereof which is evaluated by an evaluating method as set forth in claim 1 and distinguished from a concentration of atomic vacancy in a bulk thereof.

9. An apparatus for evaluating atomic vacancy in a surface layer of a silicon wafer, comprising:

a silicon sample provided with an ultrasonic wave generating portion and an ultrasonic wave receiving portion;

a magnetic field generator for applying an external magnetic field to the silicon sample;

a refrigerator for cooling the silicon sample; and

a measuring means for detecting a difference in phase between an ultrasonic wave pulse injected from the ultrasonic wave generating portion and an ultrasonic wave pulse propagated in the silicon sample and received at the ultrasonic wave receiving portion;

wherein the ultrasonic generating portion and the ultrasonic receiving portion are respective comb-shaped electrodes formed on corresponding piezoelectric films and are formed on the same main surface of the silicon sample.

10. The evaluating apparatus as set forth in claim 9,

wherein the piezoelectric film is made of zinc oxide, aluminum nitride or polyvinylidene fluoride and the comb-shaped electrode is made of aluminum (Al) or copper (Cu).

11. The evaluating apparatus as set forth in claim 9,

wherein the silicon sample is attached to a silver plate or a silver film.

13. A method for manufacturing a silicon wafer, comprising steps of:

forming a pair of surface acoustic wave (SAW) devices which are arranged opposite to one another on the same main surface of a silicon sample;

generating an ultrasonic wave pulse from one of the surface acoustic wave (SAW) devices and propagating the ultrasonic wave pulse in a surface layer of the silicon sample while the silicon sample is cooled under a condition of an application of magnetic field, and receiving the propagated ultrasonic wave pulse at the other of the surface acoustic wave (SAW) devices, thereby measuring a difference in phase between the injected ultrasonic wave pulse and the propagated ultrasonic wave pulse; and

calculating an elastic constant C_s of the surface layer of the silicon sample based on the difference in phase and evaluating a concentration “

N”

of atomic vacancy of the surface layer of the silicon sample based on a change of the elastic constant C_s with a temperature or a change of the elastic constant C_s with an intensity of the magnetic field.

14. A silicon wafer manufactured by a manufacturing method as set forth in claim 13.