阅读说明：本技术 一种半导体材料电阻率光学测量方法 (Semiconductor material resistivity optical measurement method ) 是由 王谦 刘卫国 谭林秋 于 2019-09-24 设计创作，主要内容包括：本发明涉及一种半导体材料电阻率光学测量方法,本发明的原理为：半导体材料对光子能量大于其禁带宽度的泵浦光束吸收后产生过剩载流子,过剩载流子经辐射复合后产生光子,光子在向前后表面传输的过程中被材料重新吸收,由于重吸收系数的大小与光子能量相关,加上光子传输路径的差别,前后表面被收集和测量光致发光谱不同。光子的重新吸收主要包含本证吸收和自由载流子吸收,自由载流子吸收的大小与半导体材料的掺杂浓度相关,因此可以通过分析计算前后表面收集的光致发光谱得到半导体材料的掺杂浓度,进一步由公式计算得到其电阻率的大小。本发明弥补了传统的四探针技术需要与样品接触的缺点,提高了半导体材料电阻率的测量精度。(The invention relates to an optical measurement method for resistivity of a semiconductor material, which has the following principle: the semiconductor material absorbs the pump light beam with photon energy larger than the forbidden band width to generate excess carrier, the excess carrier is radiated and compounded to generate photon, the photon is re-absorbed by the material in the process of transmitting to the front and back surfaces, and the front and back surfaces are collected and measured with different photoluminescence spectra due to the correlation between the re-absorption coefficient and the photon energy and the difference of the photon transmission path. The reabsorption of photons mainly comprises intrinsic absorption and free carrier absorption, and the size of the free carrier absorption is related to the doping concentration of the semiconductor material, so that the doping concentration of the semiconductor material can be obtained by analyzing and calculating photoluminescence spectrums collected on the front surface and the rear surface, and the size of the resistivity of the semiconductor material is further calculated by a formula. The invention makes up the defect that the traditional four-probe technology needs to be contacted with a sample, and improves the measurement precision of the resistivity of the semiconductor material.)

1. An optical measurement method for resistivity of a semiconductor material is characterized in that: the measuring method comprises the following steps:

step 1): irradiating the pump beam with photon energy larger than the forbidden band width of the intrinsic semiconductor of the tested semiconductor to the front surface of the tested semiconductor sample to generate a photoluminescence signal;

step 2): placing signal collecting devices on the front surface and the rear surface of the sample, simultaneously collecting photoluminescence signals transmitted to the front surface and the rear surface, obtaining photoluminescence spectrums through a spectrum analysis device, and recording the photoluminescence spectrums obtained on the front surface and the rear surface as

step 3): for the above photoluminescence spectrum

according to the formula

2. The optical measurement method of resistivity of semiconductor material according to claim 1, characterized in that: the signal collecting device is a paraboloidal mirror or an optical lens.

3. Optical measurement method of resistivity of semiconductor material according to claim 1 or 2, characterized in that: the spectrum analysis device is a combination of a monochromator and a photomultiplier detector or a spectrometer, and the equipment models and parameter settings of the front signal collection device and the rear signal collection device of the sample are kept consistent.

Technical Field

The invention relates to an optical measurement method for resistivity of a semiconductor material.

Background

The resistivity of a semiconductor material is closely related to parameters such as series resistance, capacitance and threshold voltage of a semiconductor device, and is a very important parameter. In order to ensure that the semiconductor material can be effectively used for devices and improve the stability and yield of the devices, accurate and quick nondestructive measurement characterization needs to be carried out on the semiconductor material. The resistivity measuring method of the semiconductor material which is most commonly used in the industry at present is a four-probe technology. However, since this technique needs to be in contact with a sample to be measured during measurement, damage to the surface of the material is inevitable, and measurement errors are increased. Meanwhile, the probe has a large sampling volume, so that the application of the probe in high-resolution two-dimensional imaging measurement is limited.

Disclosure of Invention

The invention provides an optical measuring method for resistivity of a semiconductor material, aiming at solving the problems that the surface of the material is damaged, the measuring error is increased and the sampling volume of a probe is larger in the existing semiconductor material resistivity measuring technology.

In order to solve the problems in the prior art, the technical scheme of the invention is as follows:

an optical measurement method for resistivity of a semiconductor material comprises the following steps:

step 1): irradiating the pump beam with photon energy larger than the forbidden band width of the intrinsic semiconductor of the tested semiconductor to the front surface of the tested semiconductor sample to generate a photoluminescence signal;

step 2): placing signal collecting devices on the front surface and the rear surface of the sample, simultaneously collecting photoluminescence signals transmitted to the front surface and the rear surface, obtaining photoluminescence spectrums through a spectrum analysis device, and recording the photoluminescence spectrums obtained on the front surface and the rear surface as

And

step 3): for the above photoluminescence spectrum

And

and (3) carrying out processing calculation to obtain the resistivity of the semiconductor material:

according to the formula

Performing calculation according to formula

Fitting S by a polynomial_eAnd calculating the relation data of the resistivity rho of the semiconductor material to be detected and the wavelength lambda. Wherein R is_fAnd R_bRespectively the reflectivity of photoluminescence signals on the front and back surfaces of a sample, h v is the photon energy of pump light, C is a constant, L is the thickness of a measured semiconductor material, and alpha₀Respectively, the intrinsic absorption coefficient of the semiconductor material to be tested on the photoluminescence signal, q is the electron electric quantity, and mu is the mobility of electrons or holes.

Further, the signal collecting device is a parabolic mirror or an optical lens.

Furthermore, the spectrum analysis device is a combination of a monochromator and a photomultiplier detector or a spectrometer, and the equipment models and parameter settings of the front and rear signal collection devices of the sample are kept consistent.

Compared with the prior art, the invention has the following advantages:

1) the method adopts an optical non-contact method to measure the resistivity of the semiconductor material, does not damage the measured material and does not increase the measurement error;

2) the invention adopts the laser as the pumping light source, has small volume, can measure the local micro-area of the semiconductor material and can carry out high-resolution imaging on the resistivity of the semiconductor material through two-dimensional scanning.

3) The measurement process is not influenced by the system response, so that the measurement precision of the resistivity of the semiconductor material is improved.

Drawings

FIG. 1 is a schematic structural diagram of a measuring device according to the present invention;

FIG. 2 is a calculated photoluminescence spectrum collected from the front and back surfaces according to the invention

And

FIG. 3 is a graph of S calculated according to the present invention_e；

FIG. 4 is a graph of resistivity ρ calculated in accordance with the present invention;

FIG. 5 is a schematic structural diagram of another measuring device according to the present invention.

The reference numbers are as follows:

the device comprises a function generator 1, a pumping light source 2, a reflecting mirror 3, a focusing lens 4, a sample 5, a front parabolic mirror 6, a first optical filter 7, a first monochromator 8, a photomultiplier detector 9, a first phase-locked amplifier 10, a rear parabolic mirror 11, a second optical filter 12, a second monochromator 13, a photomultiplier detector 14, a second phase-locked amplifier 15, a computer 16, a first spectrometer 17 and a second spectrometer 18.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The principle of the invention is as follows:

the semiconductor material absorbs the pump light beam with photon energy larger than the forbidden band width to generate excess carrier, the excess carrier is radiated and compounded to generate photon, the photon is re-absorbed by the material in the process of transmitting to the front and back surfaces, and the front and back surfaces are collected and measured with different photoluminescence spectra due to the correlation between the re-absorption coefficient and the photon energy and the difference of the photon transmission path. The reabsorption of photons mainly comprises intrinsic absorption and free carrier absorption, and the size of the free carrier absorption is related to the doping concentration of the semiconductor material, so that the doping concentration of the semiconductor material can be obtained by analyzing and calculating photoluminescence spectrums collected on the front surface and the rear surface, and a formula is further used for obtaining the doping concentration of the semiconductor material

And calculating to obtain the resistivity of the alloy. The invention makes up the defect that the traditional four-probe technology needs to be contacted with a sample, and improves the measurement precision of the resistivity of the semiconductor material.

Assuming that the photoluminescence spectra obtained by front and back surface measurements are

Andorder to

Then

Order to

The above formula is simplified into

exp(-αL)＝K(1+R_bexp(-2αL)) (2)

Wherein I₀Alpha is the absorption coefficient, which is the in-situ photoluminescence spectrum when photons are not transmitted.

α(λ)＝α₀+α_FCA＝α₀+Cλ³N_dop (3)

Wherein alpha is₀And alpha_FCARespectively, the intrinsic absorption coefficient and the free carrier absorption coefficient, C is a constant, N_dopIs the doping concentration of the semiconductor material.

The formula (3) is brought into the formula (2) to obtain

Relating doping concentration to resistivityBrought into the above formula to obtain

And calculating the resistivity of the semiconductor material through polynomial fitting.

The invention provides an optical measurement method for resistivity of a semiconductor material, which comprises the following specific steps:

step 1): irradiating the pump beam with photon energy larger than the forbidden band width of the intrinsic semiconductor of the tested semiconductor to the front surface of the tested semiconductor sample to generate a photoluminescence signal;

step 2): placing signal collecting devices on the front surface and the rear surface of the sample, simultaneously collecting photoluminescence signals transmitted to the front surface and the rear surface, obtaining photoluminescence spectrums through a spectrum analysis device, and recording the photoluminescence spectrums obtained on the front surface and the rear surface as

And

step 3): for the above photoluminescence spectrum

Andand (3) carrying out processing calculation to obtain the resistivity of the semiconductor material:

the measured photoluminescence spectrum is expressed according to the formula

Performing calculation according to formula

Fitting S by a polynomial_eAnd calculating the relation data of the resistivity rho of the semiconductor material to be detected and the wavelength lambda. R_fAnd R_bRespectively the reflectivity of photoluminescence signals on the front and back surfaces of a sample, h v is the photon energy of pump light, C is a constant, L is the thickness of a measured semiconductor material, and alpha₀Respectively, the intrinsic absorption coefficient of the semiconductor material to be tested on the photoluminescence signal, q is the electron electric quantity, and mu is the mobility of electrons or holes.