CN102376519B - Ion implantation dosage detection control method - Google Patents

Abstract

The invention discloses an ion implantation dosage detection control method, belonging to the plasma immersion implantation dosage detection technology field. The method comprises the following steps: measuring a plasma characteristic parameter, particle ingredients in a plasma, and particle content of each ingredient; equating quality of all ions and radicals in the plasma as same quality; equating electrically charged amounts of all ions and radicals in the plasma as a same electrically charged amount; when a plasma object implantation dosage is determined, by utilizing the quasistatic Child-Langmuir sheath implantation model theory, calculating an implantation technology time of the object implantation dosage. According to the ion implantation dosage detection control method of the present invention, a plurality of charged ion detection problems existed in a present ion implantation dosage detection method can be overcome, and the method can be used for implantation process flow control of a plasma immersion implantation machine.

Description

A kind of ion implantation dosage detection control method

Technical field

The present invention relates to the plasma immersion injection technique, particularly relate to a kind of ion implantation dosage detection control method that plasma immersion injects that can be used for.

Background technology

In semiconductor technology, the impurity doping techniques of main flow all adopts beamline ion implanters injection technique (Ion Implantation, II), this method is to produce plasma by ion source, by mass spectral analysis, required ion component is extracted again to, ion is accelerated to certain energy and is injected into (as silicon chip) in semiconductor chip.This method needs complicated mass spectral analysis and scanning means, and injection efficiency is low, complex structure, and cost is high.

Along with further dwindling of integrated circuit characteristic size, ion implantation energy need to further be reduced to a kilo electron volt following (inferior KeV), yet ion beam energy there will be the series of negative effects such as line dispersion, uniformity variation, the further reduction of efficiency after reducing.Thereby in recent years proposed novel plasma immersion injection technique (Plasma Immersion Ion Implantation, PIII) and avoided above problem.Plasma immersion injects semiconductor chip is placed on the electrode of negative electrode, and adds back bias voltage on this electrode.To introducing the gas needed in injected system work chamber, and system is added to power source, make to be introduced into the gas build-up of luminance of chamber by charging methods such as inductive coupled, capacitive couplings, form plasma.Owing to being added with back bias voltage on negative electrode, just having like this back bias voltage sheath layer and exist near substrate.Under the high voltage of this sheath layer accelerates, the cation in the sheath layer can and be injected in substrate through the sheath layer.The method has following advantage:

1. without extracting ion from ion source, ion being carried out to mass spectral analysis and linear the acceleration, make the structure of injection device greatly simplify, save great amount of cost;

2. this technology adopts sheath layer acceleration mechanism, and injection process is that full wafer injects, irrelevant with sizes of substrate, so this technology productive rate is high.

Therefore, the plasma immersion injection is a kind of injection technique of future generation that beamline ion implanters is injected that is hopeful very much to replace.But PIII also faces many technical challenges, injecting the ion dose Detection & Controling is one of them.

Method for dose measurement in PIII mainly contains bias current method and faraday cup detection method.Ion dose is injected in the current measurement that the bias current method flows through substrate by measurement.When plasma injects, flow through substrate currents I

I＝I _ion+I _e+I _se+I _dis+I _si， (1)

I wherein _ionfor injecting ionic current, I _efor the electric current of electron stream in plasma to substrate, I _sefor the electric current that substrate surface emission secondary electron forms, I _disfor displacement current, I _sielectric current for the formation of substrate emission secondary ion.If inject the surface density n of the ion dose of substrate _i

$n_i=\frac{1}{\mathrm{ne}}{\∫}_0^T{I}_{\mathrm{ion}}\mathrm{dt},---\left(2\right)$

Wherein n is for injecting the unit charge amount of ion band, and e is unit charge, and T is injection length.Form in five parts of substrate currents I _dis, I _si, I _eignore (displacement current be can not ignore sometimes, and it is more difficult that the bias current method is measured the injection ion dose like this) with respect to other parts than I, but the secondary electron electric current I _sebut than I _ionwant large one even more to twice, and I _sewith substrate material, bias voltage size etc. factor analysis and can't accurately determining.Form I simultaneously _ionion not merely only with a kind of quantity of electric charge, to also have the ion of ionized many times be that n in formula (2) is not unique, so the ion dose n that the bias current method records _ibe not that PIII is injected into the true ion dose in substrate, thus cannot be according to n _icontrol the PIII technological process.

The detection principle of faraday cup is identical with bias current method essence is all to measure the injection ion dose by measuring ionic current, difference is that the bias current method is usually using whole objective table as current measurement probe, and the faraday cup has an independently chamber, it is afterwards just measured that the injection ion enters this chamber.Because the Faraday cup mensuration has one independently to measure displacement current, the secondary current that chamber just can be eliminated to exist in the bias current method by the whole bag of tricks and structural design.But faraday cup detection method still can't solve multiple charged ion problem, so, although the method increases than bias current method, it is directly used in PIII and injects the ion dose detection and control still infeasible.

Summary of the invention

For dose measurement and control problem in existing PIII, this patent discloses a kind of ion dose of the injection for the plasma immersion implanter and has detected the method for controlling.Described technical scheme is as follows:

Ion implantation dosage detection control method of the present invention comprises:

Particle component in ion concentration, electron temperature and plasma in the measurement plasma and the particle content of each component;

All ions in plasma and the quality of group are equivalent to equal in quality; The electrically charged amount of all ions in plasma and group is equivalent to identical electrically charged amount;

When plasma target implantation dosage is determined, utilize quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, calculate the injection technology time of this target implantation dosage; And

When the plasma injection technology time is determined, utilize quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, calculate the injection ion dose in this injection technology time.

Ion implantation dosage detection control method of the present invention, according to the particle component in described ion concentration, electron temperature and plasma and the particle content of each component, utilize described quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, by formula T _im=N/ (f * dose _pulse), calculate injection technology time of this target implantation dosage; T wherein _imfor injection length, N is the doping content that substrate reaches, and f is the pulsed bias frequency, dose _pulseion dose for Sing plus injection substrate.

Ion implantation dosage detection control method of the present invention, according to the particle component in described ion concentration, electron temperature and plasma and the particle content of each component, utilize described quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, by formula N=T _im* f * dose _pulse, calculate the injection ion dose in this injection technology time;

T wherein _imfor injection length, N is the doping content that substrate reaches, and f is the pulsed bias frequency, dose _pulseion dose for Sing plus injection substrate.

Ion implantation dosage detection control method of the present invention, utilize mass spectrometer to measure particle component in plasma and the particle content of each component.

The beneficial effect of technical scheme provided by the invention is: ion implantation dosage detection control method of the present invention can overcome in above-mentioned PIII method for detecting dose the problem that exists multiple charged ion to detect; Can also control for the injection technology flow process of plasma immersion implanter simultaneously.

Embodiment

Because there is the shortcoming described in upper part in existing PIII method for detecting dose, this patent discloses a kind of method of injecting ion dose detection control for plasma immersion, for making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, embodiment of the present invention is described further in detail.

Ion implantation dosage detection control method of the present invention mainly utilizes quasistatic Child-Langmuir equation-Langmuir (Child-Langmuir) sheath theory, in this theory, for a kind of ion:

The thickness of plate shape sheath layer

s ₀＝(2ε ₀V ₀/en ₀) ^1/2， (3)

ε wherein ₀for hollow dielectric constant, V ₀for pulsed bias value, n ₀for plasma ion density.

Ion in plate shape sheath layer all injects the required time

T ₀≈2.7×2π/ω _pi， (4)

ω wherein _pi=(e ²n _pi/ ε ₀m _pi) ^1/2for plasma oscillation frequency, n wherein _pifor ion concentration, M _pifor mass of ion.

After adding pulsed bias, the expansion of plate shape sheath layer, become stable Child sheath layer through the long enough time-evolution.The thickness S of sheath layer now _c

$s_c=\frac{\sqrt{2}}{3}{({\mathrm{\ϵ}}_0{T}_e/e{n}_0)}^{1/2}{(2V_0/T_e)}^{3/4},---\left(5\right)$

T wherein _efor the plasma electrons temperature, unit is volt, reaches the time of stable state Child sheath layer

$T_c=3[{(\sqrt{2}/3)}^3{(2V_0/T_e)}^{3/4}-1]\mathrm{\π}/{\mathrm{\ω}}_{\mathrm{pi}},---\left(6\right)$

Wherein π is circumference ratio, ω _pifor plasma oscillation frequency, it is expressed as previously mentioned.At time t≤T _cthe time, the sheath layer does not reach stable state, now transient state sheath layer border S _tresiding position

$s_t={(\frac{2}{3}{\mathrm{\ω}}_{\mathrm{pi}}t+1)}^{1/3}{s}_0,---\left(7\right)$

Meeting pulse width T _p≤ T _cunder condition, Sing plus injects the ion dose of substrate

${\mathrm{dose}}_{\mathrm{pulse}}=n_0{s}_{T_p},---\left(8\right)$

Wherein

for T _pmoment sheath layer boundary position, dosage herein is surface density.

Injection length

T _im＝N/(f×dose _pulse)， (9)

Wherein N is the doping content that substrate reaches, and f is the pulsed bias frequency.

Implantation dosage

N＝T _im×f×dose _pulse， (10)

T _imfor injection length.

When meeting pulse width T _p>=T _cthe time, Sing plus injects the ion dose of substrate

dose _pulse＝n ₀[s _c+u _B(T _p-T _c)]

U wherein _bfor ripple nurse speed

Injection length

T _im＝N/(dose _pulse×f)， (11)

Inject metering

N＝T _im×f×dose _pulse， (12)

Above-mentioned quasistatic Child-Langmuir equation-Langmuir (Child-Langmuir) sheath theory that is.

The present invention utilizes the Implantation metering of quasistatic Child-Langmuir equation-Langmuir (Child-Langmuir) sheath theory to detect control method and specifically comprises the following steps:

Step 1: the particle content of at first measuring particle component in plasma characteristic parameters and plasma and each component.When dose measurement, at first utilize mass spectrometer or similar device to obtain particle component and the ratio of plasma; Meanwhile, utilize electrostatic probe or microwave interferometer to obtain the most basic characterisitic parameter of plasma: as ion concentration total in plasma, electron temperature etc.

Step 2: the quality of all ions in plasma and group is equivalent to same quality; The electrically charged amount of all ions in plasma and group is equivalent to same electrically charged amount.Because all equations of above-mentioned quasistatic Child-Langmuir equation-Langmuir (Child-Langmuir) sheath theory are only set up single kind of ion, and have different kinds of ions in plasma, their carried charge and quality may be all different.Therefore need quote equivalent mass M and equivalent charge Q.

In multiple mass ion the plasma system deposited, all ions equivalences are become to a quality, equivalent mass M meets

$\sqrt{M}=\underset{i}{\mathrm{\Σ}}{c}_i\sqrt{Q_i{m}_i},---\left(13\right)$

In formula

n _ibe the density of i kind ion, m _ifor i kind mass of ion, Q _iit is the carried charge of i kind ion.

The equivalence electric charge

$Q=\underset{\text{i}}{\mathrm{\Σ}}{d}_i{Q}_i,---\left(14\right)$

In formula

n is total ion concentration, can have plasma diagnosis device to obtain, d _ican be obtained or similarly install by analyzing plasma composition obtaining by mass spectrometer.Value c in this pattern (13) _ican be expressed as

$c_i=\frac{d_i}{\mathrm{\Σ}{Q}_j{d}_j},---\left(15\right)$

All use formula (13), (14) to be replaced in all places of using quality and the quantity of electric charge in formula (1) to (12).

Step 3: determine desired value, when plasma target implantation dosage is determined, utilize quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, by calculating the injection technology time of this target implantation dosage;

When the plasma injection technology time is determined, utilize quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, calculate the injection ion dose in this injection technology time.

In the process of the injection ion of concrete using plasma submergence implanter, at T _p≤ T _cin situation, when injecting in the definite situation of ion dose N, utilize formula (9) T in quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory _im=N/ (f * dose _pulse) can obtain under these process conditions needing the time T of injecting _im.Reach T in actual injection length _imthe time, stop whole technical process by control; If do not reach injection length T _im, control the continuity injection process, until injection length reaches T _imthe time till the injection technology flow process finishes.The particle component in monitoring plasma bulk properties parameter and plasma and the data such as particle content of each component at any time in cyclic process, when these data have large change, the adjusting process parameter is so that stable technical process or stop process process warning in time.

As plasma target injection length T _imwhen known, according to quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, utilize formula (10) N=T _im* f * dose _pulsecan calculate the injection ion dose in this injection technology time.

Equally, at T _p>=T _cin situation, according to formula T _im=N/ (dose _pulse* f) can calculate the injection length T when injecting ion dose and being N _im; Utilize formula N=T _im* f * dose _pulsecan calculate at injection length T _iminterior injection ion dose N.

The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (4)

1. an ion implantation dosage detection control method, is characterized in that, comprising:

Particle component in ion concentration, electron temperature and plasma in the measurement plasma and the particle content of each component;

All ions in plasma and the quality of group are equivalent to equal in quality; The electrically charged amount of all ions in plasma and group is equivalent to identical electrically charged amount;

When plasma target implantation dosage is determined, utilize quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, calculate the injection technology time of this target implantation dosage; And

When the plasma injection technology time is determined, utilize quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, calculate the injection ion dose in this injection technology time.

2. ion implantation dosage detection control method according to claim 1, it is characterized in that, according to the particle component in described ion concentration, electron temperature and plasma and the particle content of each component, utilize described quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, by formula T _im=N/ (f * dose _pulse), calculate injection technology time of this target implantation dosage; T wherein _imfor injection length, N is the doping content that substrate reaches, and f is the pulsed bias frequency, dose _pulseion dose for Sing plus injection substrate.

3. ion implantation dosage detection control method according to claim 1, it is characterized in that, according to the particle component in described ion concentration, electron temperature and plasma and the particle content of each component, utilize described quasistatic Child-Langmuir equation-Langmuir sheath layer injection model theory, by formula N=T _im* f * dose _pulse, calculate the injection ion dose in this injection technology time;

T wherein _imfor injection length, N is the doping content that substrate reaches, and f is the pulsed bias frequency, dose _pulseion dose for Sing plus injection substrate.

4. ion implantation dosage detection control method according to claim 1, is characterized in that, utilizes mass spectrometer to measure particle component in plasma and the particle content of each component.