CN105067421A - Three-dimensional stress characterizing method for TSV (Through Silicon Vias) structure based on image analysis - Google Patents

Abstract

The invention discloses a three-dimensional stress characterizing method for a TSV (Through Silicon Vias) structure based on image analysis. The three-dimensional stress characterizing method comprises the following steps: firstly, imaging the TSV structure from different angles by utilizing a high-resolution X-ray microscope, and then, acquiring three-dimensional point cloud data of the TSV structure through an image reconstructing technology; secondly, calculating the spatial three-dimensional deformation amount of each point in the point cloud data before and after the TSV structure is under the action of an external load; thirdly, calculating the three-dimensional stress state of each point in the TSV structure by adopting Lagrange strain tensor according to the three-dimensional deformation amount obtained in the second step. According to the method, the three-dimensional stress of the TSV structure is characterized on the basis of image signal analysis, so that the shortages of high cost and lower efficiency in conventional stress characterization can be overcome; therefore, the method is of a great significance in the failure analysis and the reliability design of a TSV structure-containing device under the action of the external load.

Description

A kind of triaxiality characterizing method of the TSV structure based on graphical analysis

Technical field

The present invention relates to semiconductor applications, especially a kind of triaxiality characterizing method of wafer TSV structure.

Background technology

The electronic manufacturing technology of leading electronics manufacturing follows " Moore's Law " (number of circuit integrated in integrated circuit (IC) chip, just doubled every 18 months) that nineteen sixty-five proposes always to be developed.But under the lasting promotion of miniaturization, multi-functional, low cost and low-power consumption, characteristic dimension in current two dimension (2D) electronic manufacture is day by day close to physics limit, make the integrated more high density of one chip and multi-purpose device further difficult, cost of development is also increased sharply, so there are the new ideas of " surmounting mole (MorethanMoore) ".According to international semiconductor Technology Roadmap (InternationalTechnologyRoadmapofSemiconductor, ITRS) address prediction, manufactures the first-selected solution moved towards three-dimensional (3D) Integrated manufacture and be considered to surmount Moore's Law, boost device performance and cost performance at present from 2D.

Integrated in order to realize chip 3D, chip needs the interconnection carrying out vertical direction, wherein the Main Function of " silicon through hole " (ThroughSiliconVia, TSV) is the chip interconnects will be stacked up at vertical direction, plays the effect such as signal conduction and heat transfer.Relative to traditional pin interconnection mode, TSV interconnection path shortens, and is conducive to reducing signal delay and power attenuation, increases integrated level and bandwidth (in same size can integrated more function element) simultaneously.As can be seen here, TSV structure has become the typical structure unit of 3D integrated technology, therefore carries out the research for TSV structure, has great importance to the microelectric technique of new generation realizing being integrated into three-dimensional representative.

Because TSV structure parameter is relevant to manufacturing process flow, the TSV manufacturing process of current main flow is clear and definite: (1) etches TSV blind hole in wafer side by deep reaction ion etching technology (DeepReactiveIonEtching, DRIE).In order to improve the step coverage of subsequent technique insulating layer deposition, general TSV sidewall is carved into the slight taper of 83 ~ 89 degree; (2) on the hole wall etched, low-pressure chemical vapor deposition (Semi-AtmosphereChemicalVaporDeposition is utilized, SACVD) or low-temperature ion strengthen chemical vapor deposition (PlasmaEnhancedChemicalVaporDeposition, PECVD) generate silicon dioxide (SiO ₂) insulation course; (3) at SiO ₂by physical vapour deposition (PVD) (PhysicalVaporDeposition, PVD) diffusion impervious layer (Ti or Ta or its nitride) on layer, then deposit one deck copper (Cu) Seed Layer over the barrier layer again; (4) by electrochemical plating, Cu is filled into TSV hole; (5) annealing process, to increase the crystallite dimension of populated Cu, and makes it be evenly distributed; (6) unnecessary Cu is removed in chemical mechanical pulping polishing (ChemicalMechanicalPolishing, CMP); (7) wafer is thinning from opposite side, expose the copper of TSV, make the flexible hole of TSV blind hole.

In order to realize above-mentioned TSV fabrication processing, ensure the performance containing TSV structure device, the mechanics parameter (thermal and mechanical stress) of TSV structure needs accurate Characterization.Such as, in TSV copper facing filling process, the microcosmic material grains size of formation and the unevenness of orientation, bring the unrelieved stress of material internal, and TSV structure is subject to the constraint of Si material around simultaneously, also can bring stress in the Si material around TSV.In annealing process and device military service process, be subject to temperature loading effect, due to the coefficient of thermal expansion mismatch of different materials in TSV structure, produce thermal stress.Thermal stress and unrelieved stress superposition may cause device to occur, and layering, cracking, hole, copper post such as to extrude at a series of integrity problem.Stress also can cause Carrier Profile to change in addition, brings device electric property to decline.Therefore these stress need to characterize, and to help design " threat district " (KeepOutZone, KOZ), make functional circuit away from this " threat district ", thus improve the service life of device.

In recent years, lot of domestic and foreign researchist, from analogue simulation and experimental viewpoint, has carried out large quantifier elimination to the sign of the mechanics parameter (stress) of TSV structure.

Document is had to pass through to measure the curvature of silicon wafer warpage, then Stoney formulae discovery plane stress state is utilized, because curvature can change along with temperature loading, the method can obtain the curve (hysteresis loop) of temperature-wafer Curvature varying, therefore temperature variant stress value can be obtained, but the method can only carry out overall mean stress sign, actual stress distribution can not be provided; Utilize the relation that lattice phonon vibrates and strains, there is document by raman microspectroscopy microscope (Micro-RamanSpectroscopy, μ RS) measure the translation (Raman frequency shift) of lambda1-wavelength, obtain material lattice dependent variable, then stress distribution is calculated by the Young modulus of material, because Raman microscope can not obtain the spectrum information of metal material, therefore the method directly can not measure the Cu structural stress of TSV, the stress state of Si can only be measured, and then extrapolate the Cu stress state of TSV, the method can only characterization of surfaces stress state simultaneously.Due to the existence strained in structure, the lattice parameter of material can be changed, X-ray diffraction instrument can measure lattice parameter according to Bragg'slaw, thus the sign of stress is obtained by the strain calculated, but the method needs the sample of setup test, the stress state of possibility change structure in the process of sample preparation.Although can be obtained the incident ray of high-penetrability by synchrotron, thus the stress that can realize under harmless condition characterizes, and testing cost is high.Bibliographical information can record the stress state of film by resonance method, but the stress state of membrane structure and TSV structure exists essential difference.The method of testing of these stress above-mentioned, is also present in corresponding deficiency for TSV structure, and therefore, the stress characterizing method of TSV structure still needs further research.

Summary of the invention

The invention provides the triaxiality characterizing method of the TSV structure that a kind of cost is low, efficiency is high.

For achieving the above object, technical scheme of the present invention is as follows:

Based on a triaxiality characterizing method for the TSV structure of graphical analysis, comprise the steps:

Step one, utilize high score rate X-ray microscope, from different perspectives imaging is carried out to TSV structure, then obtained the three-dimensional structure cloud data of TSV structure by image reconstruction technique;

Step 2, calculate TSV structure before and after external load function, in above-mentioned cloud data each point space three-dimensional deflection;

Step 3, the three-dimension deformation-quantity obtained according to step 2, adopt Lagrange strain tensor to calculate the three-dimensional stress constraint of each point in TSV structure.

Wherein, in step one, three-dimensional structure cloud data, except spatial information, also comprises image intensity information I and reflects the energy of X-ray through TSV structure.

Wherein, in step 2, before imposed load, for the arbitrfary point of TSV structure, the region of search in the TSV structure after imposed load, searches for maximally related point by the image intensity information I of point, obtains the point new position after deformation selected.

Wherein, step 3 is specially: first, according to the three dimensional strain amount that step 2 obtains, substitutes in formula as follows, calculates normal strain ξ and the shear strain γ of each point in TSV structure., then by the Young modulus of material, strain is changed into stress δ, τ

$\left(\begin{array}{ccc}{\mathrm{\δ}}_{xx}& {\mathrm{\τ}}_{xy}& {\mathrm{\τ}}_{xz}\\ {\mathrm{\τ}}_{yx}& {\mathrm{\δ}}_{yy}& {\mathrm{\τ}}_{yz}\\ {\mathrm{\τ}}_{zx}& {\mathrm{\τ}}_{zy}& {\mathrm{\δ}}_{zz}\end{array}\right)=E\left(\begin{array}{ccc}{\mathrm{\ξ}}_{xx}& {\mathrm{\γ}}_{xy}& {\mathrm{\γ}}_{xz}\\ {\mathrm{\γ}}_{yx}& {\mathrm{\ξ}}_{yy}& {\mathrm{\γ}}_{yz}\\ {\mathrm{\γ}}_{zx}& {\mathrm{\γ}}_{zy}& {\mathrm{\ξ}}_{zz}\end{array}\right)$

$\begin{array}{cc}{\mathrm{\ξ}}_{xx}=\frac{\∂u}{\∂x}\≈\frac{\▿u}{\▿x}& {\mathrm{\γ}}_{xy}=\frac{\∂u}{\∂y}+\frac{\∂v}{\∂x}\≈\frac{\▿u}{\▿y}+\frac{\▿v}{\▿x}\end{array}$

$\begin{array}{cc}{\mathrm{\ξ}}_{yy}=\frac{\∂v}{\∂y}\≈\frac{\▿v}{\▿y}& {\mathrm{\γ}}_{xz}=\frac{\∂u}{\∂z}+\frac{\∂w}{\∂x}\≈\frac{\▿u}{\▿z}+\frac{\▿w}{\▿x}\end{array}$

$\begin{array}{cc}{\mathrm{\ξ}}_{zz}=\frac{\∂w}{\∂z}\≈\frac{\▿w}{\▿z}& {\mathrm{\γ}}_{yz}=\frac{\∂v}{\∂z}+\frac{\∂w}{\∂y}\≈\frac{\▿v}{\▿z}+\frac{\▿w}{\▿y}\end{array}$

The invention has the beneficial effects as follows: the present invention is based on picture signal analysis to characterize TSV structure triaxiality, cost intensive, deficiency that efficiency is lower that traditional stress characterizes can be made up, to the failure analysis of the device containing TSV structure under external load function and reliability design significant.

Accompanying drawing explanation

Fig. 1 is embodiment of the present invention TSV structure three-dimension deformation-quantity instrumentation plan.

Embodiment

Below in conjunction with accompanying drawing and example, the present invention will be further described.

The present embodiment adopts high score rate X-ray microscope, from different perspectives imaging is carried out to TSV structure, then by image reconstruction technique obtain TSV structure three-dimensional structure cloud data (space each point except spatial information (x, y, z), image intensity information I is also had to reflect the energy of X-ray through TSV structure).Be subject to the inspiration of biological cell deformation, adopt Digital Cubic body corresponding technology (DigitalVolumeCorrelationTechnique, DVCT) TSV structure is calculated before and after external load function, the space three-dimensional deflection of each point in above-mentioned cloud data.As shown in Figure 1, before imposed load, for the arbitrfary point of TSV structure, region of search in TSV structure after imposed load (supposes that deflection is less, meet the reality of TSV structure under external applied load), search for maximally related point by the image intensity information I of point, namely can obtain the point new position after deformation selected, thus obtain the three-dimension deformation-quantity of the point selected.

Because TSV structure is solid structure, Lagrange strain tensor is therefore adopted to calculate the three-dimensional stress constraint of TSV structure.First, the three dimensional strain amount that can be obtained by said method, substitutes in formula as follows, calculates normal strain ξ and the shear strain γ of each point in TSV structure., then by the Young modulus of material, strain is changed into stress δ, τ.

It is worth mentioning that, Lagrange strain tensor is a symmetric matrix, as long as the therefore element of the upper trigonum of compute matrix or the element of lower trigonum.

$\left(\begin{array}{ccc}{\mathrm{\δ}}_{xx}& {\mathrm{\τ}}_{xy}& {\mathrm{\τ}}_{xz}\\ {\mathrm{\τ}}_{yx}& {\mathrm{\δ}}_{yy}& {\mathrm{\τ}}_{yz}\\ {\mathrm{\τ}}_{zx}& {\mathrm{\τ}}_{zy}& {\mathrm{\δ}}_{zz}\end{array}\right)=E\left(\begin{array}{ccc}{\mathrm{\ξ}}_{xx}& {\mathrm{\γ}}_{xy}& {\mathrm{\γ}}_{xz}\\ {\mathrm{\γ}}_{yx}& {\mathrm{\ξ}}_{yy}& {\mathrm{\γ}}_{yz}\\ {\mathrm{\γ}}_{zx}& {\mathrm{\γ}}_{zy}& {\mathrm{\ξ}}_{zz}\end{array}\right)$

$\begin{array}{cc}{\mathrm{\ξ}}_{xx}=\frac{\∂u}{\∂x}\≈\frac{\▿u}{\▿x}& {\mathrm{\γ}}_{xy}=\frac{\∂u}{\∂y}+\frac{\∂v}{\∂x}\≈\frac{\▿u}{\▿y}+\frac{\▿v}{\▿x}\end{array}$

$\begin{array}{cc}{\mathrm{\ξ}}_{yy}=\frac{\∂v}{\∂y}\≈\frac{\▿v}{\▿y}& {\mathrm{\γ}}_{xz}=\frac{\∂u}{\∂z}+\frac{\∂w}{\∂x}\≈\frac{\▿u}{\▿z}+\frac{\▿w}{\▿x}\end{array}$

$\begin{array}{cc}{\mathrm{\ξ}}_{zz}=\frac{\∂w}{\∂z}\≈\frac{\▿w}{\▿z}& {\mathrm{\γ}}_{yz}=\frac{\∂v}{\∂z}+\frac{\∂w}{\∂y}\≈\frac{\▿v}{\▿z}+\frac{\▿w}{\▿y}\end{array}.$

This TSV structure triaxiality characterizing method analyzed based on picture signal in the present embodiment, cost intensive, deficiency that efficiency is lower that traditional stress characterizes can be made up, to the failure analysis of the device containing TSV structure under external load function and reliability design significant.

Claims (4)

1., based on a triaxiality characterizing method for the TSV structure of graphical analysis, it is characterized in that, comprise the steps:

Step one, utilize high score rate X-ray microscope, from different perspectives imaging is carried out to TSV structure, then obtained the three-dimensional structure cloud data of TSV structure by image reconstruction technique;

Step 2, calculate TSV structure before and after external load function, in above-mentioned cloud data each point space three-dimensional deflection;

Step 3, the three-dimension deformation-quantity obtained according to step 2, adopt Lagrange strain tensor to calculate the three-dimensional stress constraint of each point in TSV structure.

2. the triaxiality characterizing method of TSV structure according to claim 1, is characterized in that, in step one, three-dimensional structure cloud data, except spatial information, also comprises image intensity information I and reflects the energy of X-ray through TSV structure.

3. the triaxiality characterizing method of TSV structure according to claim 2, it is characterized in that, in step 2, before imposed load, for the arbitrfary point of TSV structure, region of search in TSV structure after imposed load, searches for maximally related point by the image intensity information I of point, obtains the point new position after deformation selected.

4. the triaxiality characterizing method of TSV structure according to claim 1, it is characterized in that, step 3 is specially: first, according to the three dimensional strain amount that step 2 obtains, substitute in formula as follows, calculate normal strain ξ and the shear strain γ of each point in TSV structure, then by the Young modulus of material, strain is changed into stress δ, τ

$\left(\begin{array}{ccc}{\mathrm{\δ}}_{xx}& {\mathrm{\τ}}_{xy}& {\mathrm{\τ}}_{xz}\\ {\mathrm{\τ}}_{yx}& {\mathrm{\δ}}_{yy}& {\mathrm{\τ}}_{yz}\\ {\mathrm{\τ}}_{zx}& {\mathrm{\τ}}_{zy}& {\mathrm{\δ}}_{zz}\end{array}\right)=E\left(\begin{array}{ccc}{\mathrm{\ξ}}_{xx}& {\mathrm{\γ}}_{xy}& {\mathrm{\γ}}_{xz}\\ {\mathrm{\γ}}_{yx}& {\mathrm{\ξ}}_{yy}& {\mathrm{\γ}}_{yz}\\ {\mathrm{\γ}}_{zx}& {\mathrm{\γ}}_{zy}& {\mathrm{\ξ}}_{zz}\end{array}\right)$

$\begin{array}{cc}{\mathrm{\ξ}}_{xx}=\frac{\∂u}{\∂x}\≈\frac{\▿u}{\▿x}& {\mathrm{\γ}}_{xy}=\frac{\∂u}{\∂y}+\frac{\∂v}{\∂x}\≈\frac{\▿u}{\▿y}+\frac{\▿v}{\▿x}\end{array}$

$\begin{array}{cc}{\mathrm{\ξ}}_{yy}=\frac{\∂v}{\∂y}\≈\frac{\▿v}{\▿y}& {\mathrm{\γ}}_{xz}=\frac{\∂u}{\∂z}+\frac{\∂w}{\∂x}\≈\frac{\▿u}{\▿z}+\frac{\▿w}{\▿x}\end{array}$

$\begin{array}{cc}{\mathrm{\ξ}}_{zz}=\frac{\∂w}{\∂z}\≈\frac{\▿w}{\▿z}& {\mathrm{\γ}}_{yz}=\frac{\∂v}{\∂z}+\frac{\∂w}{\∂y}\≈\frac{\▿v}{\▿z}+\frac{\▿w}{\▿y}.\end{array}$