CN103292747B - A kind of method and device measuring FinFET side wall surfaceness - Google Patents

Abstract

The present invention relates to a kind of method and the device of measuring FinFET side wall surfaceness, device comprises: microscope, multiple Fibre Optical Sensor and back-end processing equipment, the fibre-optical probe of Fibre Optical Sensor is placed in Fin lines side wall the same side, fibre-optical probe and Fin surface distance launch incident light in collimating optical fibre critical distance; Collect the light beam through scattering, light beam is converted into electric signal and exports; Surfaceness is calculated according to this electric signal.Method of the present invention solves other surveying instruments cannot measure this problem of vertical side wall roughness, is conducive to sign prepared by Nano-structure in semiconductor preparing process, significant to integrated circuit Study on Preparation.Apparatus structure of the present invention is simple, and cost is low.Measuring system composition instrument is simple and easy to buy, and optical system measuring, without the need to using probe, does not have consumption part, advantage of lower cost.

Description

A kind of method and device measuring FinFET side wall surfaceness

Technical field:

The present invention relates to a kind of method measuring hachure surfaceness, particularly relate to a kind of method and the device that utilize the scatterometry FinFET lines side wall surfaceness of light, belong to VLSI (very large scale integrated circuit) manufacturing technology field.

Background technology:

Fin formula field effect transistor (FinField-effectTransistor; FinFET is that FinFET has outstanding inhibiting effect to short channel effect by the new device of the people such as U.S. Berkeley University professor ChenmingHu in invention in 1999.Along with Intel in 2011 announces to use FinFET technique in 22nm processor.FinFET becomes research focus again.

The electric current of FinFET is the side wall surface flowing at Fin lines, and therefore, the roughness on side wall surface has a great impact device performance.If side wall surface ratio is more coarse, can cause grid oxygen degradation, carrier mobility declines, and drive current reduces, and Leakage Current increases, and low-frequency noise increases.Therefore, the roughness reducing side wall surface is very crucial to the preparation of FinFET.And the roughness that side wall surface was measured and characterized on accurate quantitative analysis ground finds the prerequisite reducing roughness method.

In semiconductor fabrication, the surfaceness that atomic force microscope (AtomicForceMicroscope) carrys out quantitative measurment plane is passed through in the measurement of surfaceness more, and its principle is the pattern utilizing needle point and interatomic acting force to carry out characterization of surfaces.Scanning process is moved by Piezoelectric Ceramic sample, and because the dilatation amount of piezoelectric ceramics is very small, control voltage often changes 1V, and stroke only changes several nanometer.Therefore the precision of AFM measurement is very high, but this method is restricted when measuring the roughness of vertical surface, and reason has 2 points, and one is that vertical probe is difficult to touch vertical side wall with needle point; Two is that needle point itself has one fixed width and radian, even acclive side wall, needle point is also probably touched less than bottom side wall.For AFM in the limitation measuring Fin lines side wall roughness, a lot of scholar is studied, and object is the roughness making it possible to symbolize with AFM equipment side wall by various way.Such as: the people such as the Marinello of Italian Padova university, by the certain angle that tilted by print, make needle point can touch bottom side wall, characterize the roughness on side wall surface; The people such as the Martin in American I BM research centre use a kind of special needle point to obtain good side wall precision; The people such as XiaohuiTang of Catholicism Univ Louvain of Belgium utilize thinning after SOI sheet prepare Fin lines, then eroded by BOX layer, Fin lines are outwelled, side wall from vertically becoming plane, then measures side wall surfaceness with AFM.Although these methods finally can obtain side wall surfaceness, test process is complicated, has particular/special requirement, can not be commonly used to the measurement of vertical side wall surfaceness to technology and equipment.

Summary of the invention:

The present invention proposes a kind of method utilizing the loose measurement side wall roughness of light, accurately can measure vertical side wall surfaceness, and to print without special preparation requirement, when avoiding using probe, effects on surface causes damage, avoids consuming probe.

Technical scheme of the present invention is as follows: a kind of method measuring FinFET side wall surfaceness, and its step comprises:

Fibre-optical probe is placed in Fin lines side wall the same side and launches incident light;

Collect the light beam through scattering, described light beam is converted into electric signal and exports;

Measure according to this electric signal and obtain surfaceness.

Further, described fibre-optical probe and Fin lines to be measured are in same level, vertical with Fin line length direction.

Further, described fibre-optical probe and described Fin surface distance launch incident light in collimating optical fibre critical distance.

Further, described electric signal calculates the method for surfaceness and is: mirror field scattered light intensity I be converted into after electric signal with surfaceness R _qaccording to following transformation: wherein, K is the constant relevant with incident intensity and surfacing reflection coefficient, α ' ₀for specular reflection direction and surface direction angle, λ is optical wavelength, R _qfor surfaceness.

Further, when the height of described Fin lines side wall surface profile and slope distribution are gaussian shaped profile, and incident light wave length is greater than the roughness R of surface profile _qtime, mirror field scattered light intensity spatially angle is that variable becomes Gaussian distribution, wherein, and σ ²for the variance of light distribution, α is the angle of light and surface normal in mirror field.

Preferably, described fibre-optical probe adopts collimation-type optical fiber sensor.

Preferably, collect the light beam through scattering, described specular reflection direction and surface direction angle α ' ₀be 0.

Preferably, use microscope to regulate fibre-optical probe, close microscope light source when measuring and starting.

Preferably, adopt light activated element described light beam to be converted into electric signal to export.

Also propose a kind of device measuring FinFET side wall surfaceness based on measuring method the present invention, comprising: microscope, multiple Fibre Optical Sensor and a back-end processing equipment,

Described microscope is for regulating the distance between sensor probe and side wall surface;

Described Fibre Optical Sensor is for sending light beam and receiving reflected light, and described Fibre Optical Sensor is made up of optical fiber, light activated element and signal amplification circuit;

Described back-end processing equipment is used for processing the data collected, and exports the surfaceness R of tested side wall _q, described back-end processing equipment is made up of computer equipment, output unit, computing unit.

Beneficial effect of the present invention:

1) solve other surveying instruments and cannot measure this problem of vertical side wall roughness.Surface roughness measuring instrument, as atomic force microscope (AFM) has very large difficulty when measuring vertical surface, the present invention specially for vertical side wall surfaceness measurement problem and propose, be conducive to sign prepared by Nano-structure in semiconductor preparing process, significant to integrated circuit Study on Preparation.

2) avoid in traditional measurement instrument and use probes touch formula measurement means.The present invention adopts optical measurement means, avoids using probe, therefore can not cause damage to sample surfaces.

3) optical system, realizes Quick Measurement, and precision is high.

4) structure is simple, and cost is low.Measuring system composition instrument is simple and easy to buy, and optical system measuring, without the need to using probe, does not have consumption part, advantage of lower cost.

Accompanying drawing illustrates:

Fig. 1 is that the mirror field light distribution that the present invention measures rough surface in method one embodiment of FinFET side wall surfaceness becomes Gaussian distribution schematic diagram.

Fig. 2 is the relation schematic diagram that the present invention measures stochastic pattern, collimation-type and coaxial type Fibre Optical Sensor output voltage V and operating distance d in method one embodiment of FinFET side wall surfaceness.

Fig. 3 is that the present invention measures measurement mechanism schematic diagram in device one embodiment of FinFET side wall surfaceness.

Fig. 4 is that the present invention measures operation steps schematic diagram in method one embodiment of FinFET side wall surfaceness.

Wherein, 1 is fiber-optic signal generator, and 1-1 is fiber-optic signal receiver, and 1-2 is light activated element, and 2 is microscope, and 3 is fibre circuit, 4 be silicon slice under test side wall surface, 5 for silicon chip long, 6 is that silicon chip is wide, and 7 is that silicon chip is high.

Specific embodiments:

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described, be understandable that the technical scheme in the embodiment of the present invention, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those skilled in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Inventive principle

Surfaceness is generally with the root-mean-square value R of profile arithmetic average error and surfaceness _qrepresent, define the arithmetic mean of sampling unit's length 1 Internal periphery offset distance y (x) absolute value.

According to the scattering theory of light at rough surface, when light beam incides measured surface with α angle, if surface is desirable smooth, incident light produces total reflection in specular reflection direction, and reflection angle is α '.If surface is coarse, part or all of incident light produces scattering and departs from α ' angle.Therefore the Change of light energy of certain angle of space can reflect surface roughness characteristics.Reverse with regard to mirror reflection, surface is more coarse, and energy is less, thus can according to the size of its measure of the change surfaceness.

When light beam is irradiated to rough surface with α angle, form scattered field light distribution in the mirror field of light, when the height of measured surface profile and slope distribution are gaussian shaped profile, and incident light wave length is greater than the height root-mean-square value R of surface profile _qtime, mirror field light distribution spatially angle is that variable becomes Gaussian distribution, as shown in Figure 1.Mirror field light intensity (can with reference to Beckmann, Petr; Spizzichino, Andre, " Thescatteringofelectromagneticwavesfromroughsurfaces ", Norwood, MA, ArtechHouse, Inc., 1987, pp.511.) can be expressed as:

$I\left(\mathrm{\α}\right)=\frac{1}{{\left({2\mathrm{\π\σ}}^2\right)}^{1/2}}\exp [-\frac{{(\mathrm{\α}-{\mathrm{\α}}_0^{\′})}^2}{{2\mathrm{\δ}}^2}]---\left(1\right)$

σ ²for the variance of light distribution, α is the angle of light and surface normal in mirror field; α ' ₀for the beam reflection direction by laws of geometrical optics, i.e. specular reflection direction.

Can be proved by scattering theory, specular reflection direction α ' ₀on light intensity and surfaceness R _qthere is following relation:

I(α′ ₀)=Kexp[-(4πR _qcosα′ ₀/λ) ²](2)

Wherein, K is the constant relevant with incident intensity and surfacing reflection coefficient; α ' ₀for specular reflection direction and surface direction angle; λ is the wavelength of light wave; R _qfor the root-mean-square value of surfaceness.

The present invention adopts Fibre Optical Sensor as the element launching light wave and collection light wave.The incident direction of general Fibre Optical Sensor is normal incidence, i.e. specular reflection direction α ' ₀=0.Can be obtained by formula (1) and formula (2)

I(0)＝Kexp[-(4πR _q/λ) ²](3)

Can see that the light intensity that Fibre Optical Sensor receives is inversely proportional to surfaceness relation thus, and one_to_one corresponding.The present invention by measuring the light intensity in specular reflection direction, can calculate surfaceness R _q.Fibre Optical Sensor receives reflected light by receiving optical fiber, and reflected light enters photodiode, is converted to electric signal, and therefore voltage signal V can reflect surfaceness R _q.

The kind of Fibre Optical Sensor is more, and in side wall surface finish measurement, the present invention wishes to record voltage signal by sensor, and the distance d change with sensor and side to be measured is little.Otherwise distance slightly changes during measurement, measuring voltage value difference is not very large, can not realize accurate measurement.Reflection-type optical fibre sensor structure has stochastic pattern, coaxial type and collimation-type.As shown in Figure 2, horizontal ordinate V represents voltage swing in the V-d curvilinear motion of these three kinds of sensors, and ordinate d represents the distance d of side to be measured, can see, only have the V-d curvilinear motion of collimation-type more slow, within the scope of operating distance d<d03, export and do not change with d.During test, only sensor and lateral distance to be measured need be adjusted within the scope of d03.The position control of Fibre Optical Sensor is provided by the adjusting knob of test platform, the knob of the similar microscope stage of this regulating device, can regulate the position of sensor in three dimensions.

Measurement mechanism is as Fig. 3, and by microscope, Fibre Optical Sensor, back-end processing equipment forms.Wherein, 1 is fiber-optic signal generator, and 1-1 is fiber-optic signal receiver, and 1-2 is light activated element, and 2 is microscope, and 3 is fibre circuit, 4 be silicon slice under test side wall surface, 5 for silicon chip long, 6 is that silicon chip is wide, and 7 is that silicon chip is high.Microscope 2 is used for observing measured surface, and regulate the distance between sensor probe and tested sidewall, FinFET lines, at 20 ran, highly also only have hundreds of nanometer, only under high-power microscope, just can see lines location.Fibre Optical Sensor is by fiber-optic signal generator, and fiber-optic signal receiver, light activated element, amplifying circuit forms.Back-end processing equipment processes to the data collected, and exports the surfaceness R of tested side wall _q.Described microscope should be high-power microscope, and enlargement factor suggestion, more than 10000 times, clearly could see Fin lines location.Described back-end processing equipment comprises: photodiode, analog to digital converter, wave filter, waveform oscilloscope, photodiode, analog to digital converter, computing machine.

As shown in Figure 4, concrete scheme of the present invention is as follows:

1) silicon slice under test is placed on test board, find the Fin lines to be measured on silicon chip under the microscope, and slowly regulate the same side fibre-optical probe of Fibre Optical Sensor being placed in tested Fin lines side wall, namely the vertical plane on length direction is referred to, the requirement of described silicon slice under test must be clean silicon chip, surface does not have particle contaminant, otherwise can affect accuracy of measurement.

2) regulate fibre-optical probe under the microscope, make it slowly to decline, height lower than Fin bar top to be measured, and ensures that the distance of probe and measured surface is in collimating optical fibre critical distance d03, makes probe vertical with Fin bar length direction.

3) opening device, opens Fibre Optical Sensor light source, and light vertically shines side wall surface by incident optical, then through scattering by receive fiber optic receiver collect light beam, the light beam collected by optical fiber be passed to light activated element as, on photodiode.When noting test, microscope light source be closed, to reduce the impact of ambient light on measurement result.Need repetitive measurement to average and obtain the roughness of side, measure and obtain more multi-group data more than ten times.

3) light beam received is converted into voltage signal by light activated element.Voltage signal, through process such as amplifying circuits, imports computer equipment into.

4) in computing machine, existing program calculates tested Fin lines surfaceness according to importing voltage signal into, automatically can calculate the numerical value of surveyed Fin lines side wall surfaceness.

That the present invention measures measurement mechanism schematic diagram in device one embodiment of FinFET side wall surfaceness as shown in Figure 3.Preferred in the present embodiment, microscope is used for observing measured surface, and regulate the distance between sensor probe and tested sidewall, FinFET lines, at 20 ran, highly also only have hundreds of nanometer, only under high-power microscope, just can see lines location.Fibre Optical Sensor is by signal generator, and fiber-optic signal receiver, optical fiber, light activated element, amplifying circuit forms.Back-end processing equipment processes to the data collected, and exports the surfaceness R of tested side wall _q.Above-mentioned measurement light intensity requirement intensity is greater than Natural light intensity, improves measuring accuracy.Incident angle is 0 degree, i.e. vertical incidence, and reflected light also can vertical exit.Original silicon chip selects no requirement (NR), as long as silicon chip surface is clean, does not affect side wall roughness measurement result.

Claims (7)

1. measure a method for FinFET side wall surfaceness, its step comprises:

Fibre-optical probe is placed in Fin lines side wall the same side and launches incident light, described fibre-optical probe is vertical with Fin line length direction, the surface distance of described fibre-optical probe and Fin is in collimating optical fibre critical distance, and described fibre-optical probe adopts the fibre-optical probe of collimation-type optical fiber sensor;

Collect the light beam through scattering, described light beam is converted into electric signal and exports;

Measure according to this electric signal and obtain surfaceness.

2. the as claimed in claim 1 method measuring FinFET side wall surfaceness, it is characterized in that, the method that described electric signal calculates surfaceness is: mirror field scattered light intensity I be converted into after electric signal with surfaceness R _qaccording to following transformation: wherein, K is the constant relevant with incident intensity and surfacing reflection coefficient, α ' ₀for specular reflection direction and surface direction angle, λ is optical wavelength, R _qfor surfaceness.

3. the as claimed in claim 2 method measuring FinFET side wall surfaceness, is characterized in that, when the height of described Fin lines side wall surface profile and slope distribution are gaussian shaped profile, and incident light wave length is greater than the roughness R of surface profile _qtime, mirror field scattered light intensity spatially angle is that variable becomes Gaussian distribution, wherein, and σ ²for the variance of light distribution, α is the angle of light and surface normal in mirror field.

4. the method measuring FinFET side wall surfaceness as claimed in claim 2, is characterized in that, collect the light beam through scattering, described specular reflection direction and surface direction angle α ' ₀be 0.

5. the method measuring FinFET side wall surfaceness as claimed in claim 1, is characterized in that, uses microscope to regulate fibre-optical probe, closes microscope light source when measuring and starting.

6. the method measuring FinFET side wall surfaceness as claimed in claim 1, is characterized in that, adopts light activated element described light beam to be converted into electric signal and exports.

7. measure a device for FinFET side wall surfaceness, comprising: microscope, multiple Fibre Optical Sensor and back-end processing equipment, is characterized in that,

Described microscope is for regulating the distance between sensor probe and side wall surface;

Described Fibre Optical Sensor is for sending light beam and receiving reflected light, and described Fibre Optical Sensor is made up of optical fiber, light activated element and signal amplification circuit;

Described back-end processing equipment is used for processing the data collected, and exports the surfaceness R of tested side wall _q, described back-end processing equipment is made up of computer equipment, output unit, computing unit.