Method for control of defectiveness and resilient deformation in semiconductor heterostructures layers

FIELD: physics.

SUBSTANCE: with the help of c X-ray diffractometry using a grazing primary X-ray flux one obtains an asymmetric reflection from crystallographic planes forming the largest angle with the substrate - epitaxial layer interface surface and determines deformation in epitaxial layers by change of the distance between the diffraction maximums from the epitaxial layer and the subsrtrate; one applies single-chip X-ray diffractometry with a quasiparallel X-ray flux with the flux total divergence and convergence = 12'-24'; the maximum reflection is obtained by way of the heterostructure azimuth turn round a normal to the heterostructure surface; the angle of the X-ray flux drop onto the surface is within the range of 2.5-9°; then one proceeds with the Bragg angle correction by way of changing the angle of the primary X-ray flux drop onto the crystallographic plane coinciding with the heterostructure surface until obtainment of the maximum reflection; using the system of crystallographic planes of epitaxial layers growth one obtains a simultaneous reflection from similar systems of crystallographic planes of growing epitaxial layers and the substrate, among other things, recording existence of an intermediate layer between them.

EFFECT: extension of the array of tasks solved during heterostructures study.

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The present invention relates to semiconductor microelectronics, nanotechnology and can be used for control in the manufacture of class heterostructure, including modern-looking structure in the wide gap materials AlGaN/GaN and SOI structure with nanometrovymi layers, and the formation of the active and passive elements of the integrated circuits and discrete devices.

To study single-crystal heterogeneity AlGaN/GaN with nanoscale layers known two - and three-chip x-ray diffraction. Almost x-ray diffractometry is based on a comparison of the analyzed single-crystal sample with a perfect single crystal. The method is implemented in such a way that one of the crystals (often a perfect single crystal, the crystal - monochromator made of crystal with a high degree of perfection) remains stationary while the other rotates around an axis lying in the analyzed crystallographic plane and in the perpendicular Breggovskoi plane. When this is fixed, the intensity of the reflected light depending on the angle of rotation of a rotating crystal. The investigated crystal should be placed in the position Laevskoj or Bragg diffraction. In the case of small rotations of the analyzed single crystal with the so-called the rocking curves (interference maxima of reflection). When the disorientation of the two crystals is observed broadening of the curve of the swing, and when in the investigated crystal has some defective parts, rocking curves are obtained in the form of multiple maxima. On the angular distance between the peaks is possible to determine the relative change of the lattice parameters of the investigated single-crystal sample

To study these heterostructures with nanoscale layers in the method-analogue as a monochromator was used monocrystal Germany in the reflecting position (004) (Rimanov, Iasbet, Gbollie. "Double crystal x-ray diffractometry and study the relationship of perfection of the crystal structure of nanoscale layers and electrical properties in pseudobinary heterogeneity Al_xGa_(1-x)As/In_yGa_(1-y)As crystallography, 2008, volume 53, No. 2, s-213). As an x-ray source was used x-ray tube with copper anode capacity of 1.2 kW. Rocking curves from heterostructures was filmed Θ/2Θ-scan in step-by-step mode with the given statistics of the signal in each measurement point. The accuracy of intensity measurements from the angular dependence of the diffracted x-rays was no worse than 7%. To suppress diffuse background in this version of the double crystal ispolzovalas the system of special slots. In particular, through the use of a narrow receiving slit was made basic separation of the coherent and diffuse component of the total scattering, thereby increasing the dynamic range of the measured intensity of the diffraction scattering, which, in turn, allowed us to analyze heterostructures with such thin layers, without using a moving x-ray beam.

The disadvantages of the method are similar:

- the extreme complexity of the method (placing two crystals relative to each other and removing the 1st curve swing may require 5-6 hours of time);

- information obtained from one set of crystallographic planes, which excludes the possibility to obtain information about the deformation of the entire crystal lattice of the individual layers in full. In this case, reflection is used only on one system of the Bragg planes (400), parallel to the surface of the heterostructure, and to evaluate the elastic deformation of the lattice in the growing epitaxial layers and heterostructures require information mainly about the change of the lattice parameter in the azimuthal direction, thus, the elastic deformation in the epitaxial layers and heterostructures almost impossible to estimate;

- requires the use of complex and powerful x-ray equipment

The quality is great prototype of the selected x-ray diffractometry using primary moving the x-ray beam, which is recommended to evaluate the crystallographic mismatch epitaxial layer and the monocrystalline substrate (Don, Bchannel. "High-resolution x-ray diffractometry and topography", Moscow, "Science", 2002, S. 72-77) to obtain the asymmetric reflections from crystallographic planes, which is the largest angle with the surface of the interface substrate - epitaxial layer and determine the strain in the epitaxial layers by changing the distance between the interference maxima from the epitaxial layer and the substrate. The measurement is carried out in the geometry of incidence or glide, i.e. the separation of the peaks of maximum reflection from the substrate and the layer is carried out by rotating the substrate 180° around the normal to the surface of the substrate with the receipt of two peaks in two geometries:

For incidence:

For a moving reflection:

where θ is the Bragg angle, φ is the angle between the reflecting plane and the sample surface.

This measurement allows to separately determine δθ and δφ, which in turn allows to determine the parameters of a fully relaksirano lattice epitaxial layer. Through complicated calculations through δθ and δφ, the lattice parameters of the substrate and epitaxial layer using the forms of the crystals for the interplanar distances and angles tetragonal lattice are determined by the relaxation of the lattice layer relative to the substrate.

The advantage of this method compared with analog is that this method allows to determine the mismatch of lattices as parallel to the interface substrate - epitaxial layer, and perpendicular to the interface, i.e. the method allows for a number of cases to calculate the total elastic deformation of the crystal lattice of the epitaxial layers, to obtain some data on the average density of dislocations in the layers. In addition, the greater the angle between the crystallographic plane, the reflection of which is analyzed, and a plane coincident with the surface of the sample, the more accurate measurement of the rotation angle of the reference plane relative to the Bragg plane, i.e. the greater the accuracy of the installation crystallographic plane in the reflecting position, i.e. the greater the accuracy of the method.

Use the same method of two - and three-chip diffraction.

The disadvantages of this method is:

- the high complexity of the measurement process, typical for two - and three-chip x-ray diffraction, and in this case, the complexity increases because the measurement process is the rotation of the sample by 180° and, most likely, will require adjustment of the position of the sample after reinstalling when shooting;

- increased requirements in preparing analyses the sample has been created - the surface of the substrate should clearly enough to coincide with a certain crystallographic plane;

- increasing complexity of the process applied to semiconductor structures due to the precision installation of heterostructures on basic slice;

- the possibility of errors when rotating the sample by 180° requires the use of complex and powerful x-ray equipment;

- the use of any cracks (even if tehcnically scheme you at the last stage of the primary beam to supply additional compressive monochromator, is still narrow slit in front of the detector that tungsten gives a General convergence-divergence 10 angular minutes due to the diffraction at the edge of the slit) negates all efforts to form a strictly parallel to the primary beam;

almost very considerable difficulty in determining the relaxation transition layers in heterostructures.

Thus, this method is time consuming, requires the use of powerful x-ray equipment, which, in turn, requires the implementation of it only in specially equipped premises, does not provide the visual information on the crystallographic perfection of the individual layers in heterostructures. For control of multilayer heterostructures can be optimal.

The technical result is Vashego of the invention is a sharp decline in labour input, the extension of complex tasks for heterostructures, in particular, the analysis of elastic strains in several layers of the heterostructure, the possibility of detecting and monitoring the transition layer between the substrate and the epitaxial layer, improving the accuracy of measurements analyzed angles, the use of low-power equipment with low-level x-ray radiation, which in turn does not require work in specially equipped premises, reducing the cost of the equipment used, enhance the visibility, and therefore informative way.

The technical result is achieved by the fact that in the known method of monitoring defects of epitaxial single crystal layers, including the measurement using x-ray diffractometry using a moving primary x-ray beam with obtaining asymmetric reflections from crystallographic planes, which is the largest angle with the surface of the interface substrate-epitaxial layer, and the definition of strain in the epitaxial layers by changing the distance between the interference maxima from the epitaxial layer and substrate use of single crystal x-ray diffractometry with quasi parallel x-ray beam with a total divergence and convergence of the beam 12'-24', get Maxim is the emotional reflection by azimuthal rotation of the heterostructure around the normal to its surface, when the angle of incidence of the x-ray beam to the surface should be in the range of 2.5-9°, then make the adjustment of the Bragg angle by changing the angle of incidence of the primary x-ray beam on the crystallographic plane coinciding with the surface of the heterostructure, to obtain maximum reflection and, using the system of crystallographic planes, which showed the growth of epitaxial layers, receive simultaneous reflections from similar systems crystallographic planes of the growing epitaxial layers and substrates, including locking the presence of a transition layer between them, and to obtain maximum reflection by azimuthal rotation heterostructure around the normal to its surface in the case sirosonic heterostructure AlGaN/GaN Bragg plane enter the direction <110>, for SPS-structures impose the direction <331>.

In the proposed method, first of all, single-chip diffractometry, which dramatically reduces the complexity of the measurement process, because it does not require strict placing the analyzed sample with respect to the crystal-monochromator, and also dramatically reduced the cost and complexity of the equipment used (cost per order), in particular does not require the use of special slits.

Used in pre the proposed method quasi parallel x-ray beam with divergence and convergence 12'-24' (a well-collimated beam allows for low power consumption to be reflected in a wide intensity range, and the use of detector high sensitivity allows you to watch Blestyashie peaks. This dramatically increases the sensitivity of the method and significantly expands its capabilities (resolution of the peaks with Δθ is 1.5° or less up to 0,1°). This, in turn, allows you to record reflections from planes with minimal turn relative to each other, i.e. increases the sensitivity of the method. The proposed method allows to analyze multilayer structure where the lattice constant incoming layers differ from each other by a small increment, for example, a heterostructure type AlGaN/GaN/AlN lattice constant for AlN and GaN, respectively: a-axis_aboutfor AlN - 3,112 And, for GaN - 3,189 A; - axis c_aboutfor AlN - 4,982 And, for GaN - 5,185 A. It is also possible to resolve the interference maxima of the diffraction and analyze the transition layer between the substrate and the epitaxial layer, for example, in SOS structures. Thus, when using more simple in operation and inexpensive single-chip diffraction proposed method essentially provides method-analogue and the prototype method - two - and three-chip diffraction, complex and time-consuming methods.

In the proposed method, to obtain maximum reflection by azimuthal rotation of the heterostructure around the normal to its surface is involved in the Bragg plane entered certain crystallographic directions: for wide band gap heterostructure AlGaN/GaN direction < 110>and for CND-structures - direction <331>. This ensures that all crystallographic directions <113> <111> and <224> will be in the Bragg plane, which, in turn, will greatly simplify the orientation of the investigated heterostructures and greatly reduce the labor intensity of the process.

In the proposed method, by further adjustment of the Bragg angle of the primary x-ray beam to obtain reflections from the system of crystallographic planes, which was the initial growth of epitaxial layers, it is possible to obtain simultaneously the reflection from a system similar to the crystallographic planes of the substrate, transition and epitaxial layers without changing the position of the tube and detector. In the case of larger lattice mismatch layer and the substrate, as, for example, GaN on sapphire (13,9%), epitaxial island growth begins crystallographic directions, providing a minimal lattice divergence. In particular, the growth of GaN layers on sapphire substrates with the orientation of the surface (0001) by means of high-resolution electron transmission microscopy at the boundary between the substrate and the growing layer were found intermediate layer {10Ĭ0} GaN and {112-0} sapphire, and then the overall growth of the layer was already going in the direction of <0001> (.Ambacher "Growth and applications of group III-nitrides" / J.Phys. D.Appi Phys., 1998, V.31, P.2653-2710). Focus on the system it crystallographic planes, which is the initial islet growth of epitaxial films, allows to obtain reflections from systems similar crystallographic planes simultaneously substrate, a transition layer and the epitaxial layer, and the use of other claimed features to allow these Blestyashie interference peaks in the diffraction patterns.

Thus, the proposed method uses a number of new elements (single-crystal x-ray diffractometry with quasi parallel x-ray beam with a total divergence and convergence of the beam 12-24 minutes of arc; the use of the system of crystallographic planes, which was the initial growth of epitaxial layers and the analysis of the diffraction interference pattern), which provides in comparison with the prototype of a sharp decline in the labor process when expanding complex of tasks for the analysis of semiconductor heterostructures with submicron and nanometrovymi transition layers.

The present invention also essential, as it provides compared to analogue and prototype:

- sharp to reduce the complexity of process control;

- the possibility of detecting and monitoring the transition layer between the substrate and epitaxial layer on the planes, which is the growth of the epitaxial layer is formed and where the transition layer, and not only on the basic planes;

- improving the measurement accuracy of the analyzed corners;

- ability to use low-power devices, which in turn does not require work in specially equipped premises;

the cost of used equipment;

- enhance the visibility, and therefore informative way.

The proposed method is proved to be optimal for control of such modern and advanced semiconductor heterostructures, as wide-gap heterostructure AlGaN/GaN and SOS strucutre, which are currently widely used for manufacture of modern semiconductor IC and discrete devices for various purposes, in particular the widespread photodiodes on AlGaN/GaN.

Thus, the claimed method meets the criterion of "inventive step", since all the elements of novelty in this application does not imply evidence for specialists. It should be noted that it is the combination of all the proposed elements with a known schema-incidence x-ray beam on the analyzed surface gives a fundamentally new build testing method of semiconductor heterostructures with nanometrovymi layers.

Examples 1. In the accordance with the claimed method was carried out control of defects and elastic deformation in the layers of the band structure of GaN/sapphire layer thickness of 3 μm GaN (table 1. 2). The original surface of the sapphire substrate was almost the same crystallographic plane sapphire (0001), misorientation was 0.5°. Epitaxial layers were grown using the MOS-hydride epitaxy (MOCVD). The testing was carried out on single-crystal x-ray diffractometer. Used x-ray radiation CuK_αthe primary was used quasiparallel beam of x-rays with a total divergence in the range of 12'-24', which was fueled by the use of capillary x-ray optics - lenses kumacheva. Analyzed the heterostructure was placed on the object table setup. As the plane reflection sapphire was selected crystallographic plane (112-0). Calculate the angle of incidence of the primary x-ray beam α on the surface of the sample (basal plane (0001) thus, to obtain a Bragg angle with the plane of the initial growth of GaN layers (112-0) (figure 1). In this case, this angle is 8,83°, the center of the detector in this case is installed in position 57° (θ). The program takes into account that the angle of incidence is not Breggovskom angle itself performs the precision computations. The coincidence, when the direction <112-0> lies in the Bragg plane, the resulting interference peaks for a given plane at an angle 29,2° in the direction of the detector, to the which is Breggovskom angle to planes (112-0). To obtain maximum reflection by azimuthal step-by-step rotations of the input clearly the direction <112-0> in the Bragg plane, and thus we get the maximum of the interference peak from the sapphire substrate. Then make the adjustment, since the reference plane is not exactly the same as kristallograficheskoi plane (0001), by changing the position of the tube in small intervals, thus obtaining the maximum peak only from sapphire.

Further, in order to get the reflection from the plane (112-0) already epitaxial GaN layer, begin to reduce the angle θ, so that similar crystallographic plane came out of the reflection, in the peak of sapphire on the diffraction curve begins to decrease, and escalates to the maximum peak position from planes (112-0) GaN. Set the middle position when there are two peaks from the substrate and epitaxial layer at a time. Next, determine the structure of the intermediate layer. To do this, hold step-by-step tilt Bragg plane to obtain the interference maximum of the intermediate layer, which is offset from the peaks from the substrate and epitaxial layer toward larger angles. This suggests that the crystal lattice of the intermediate layer is in a state of compression. Width of the peak from the GaN layer defined with Epen imperfections of the crystal lattice of the layer.

The results of the declared parameters of the method, in particular the angle of incidence of the x-ray beam to the surface in the study of wide-gap heterostructures, are summarized in Tables 1 and 2 (paragraph 2).

Example. 2. In accordance with the claimed method was carried out control of defects and elastic deformation in the layers of silicon SOS structures with the thickness of the epitaxial layer of 0.3 μm. The original surface of the sapphire substrate was almost the same crystallographic plane sapphire (1Ĭ02), misorientation was 1°. When using the crystallographic plane sapphire (1Ĭ02) (r-plane) distance between layers of oxygen atoms sapphire is close in magnitude to the interplanar distance between crystallographic planes (100) silicon. Control as in example 1 was carried out on single-crystal x-ray diffractometer. Used x-ray Cu K_α. As the primary was used quasiparallel beam of x-rays with a total divergence in the range 12-24, which was fueled by the use of capillary x-ray optics - lenses kumacheva. Analyzed the heterostructure was placed on the object table setup. As the plane reflection sapphire was selected crystallographic plane (331). Calculate the angle of incidence of the primary x-ray beam is and the sample surface (1Ĭ02) thus, to get a Bragg angle with the plane (331). In this case, this angle is 12,97°, the detector is in this case mounted in position 60° (θ). The resulting interference peak for the plane (331). To obtain maximum reflection by azimuthal step-by-step rotations of the input clearly the direction <331> in the Bragg plane, and thus we get the maximum of the interference peak from the sapphire substrate. Then make the adjustment, because the base plane is not precisely coincide with the crystallographic plane (1Ĭ02), by changing the position of the tube in small intervals and received the maximum of the interference peak at a diffraction curve from sapphire.

To obtain reflections from the crystallographic plane (113) silicon (plane growth is far from a reference plane - height plane (123) sapphire is gradually moving in the plane (113) silicon) set the angle of incidence of the x-ray beam to the surface of the heterostructure α=2,87° and the resulting interference peak from this plane of silicon and a transition layer between the substrate and the epitaxial layer. Position when the spiking from the transitional and epitaxial layers, is set by the angle of the tube α (Figure 2). The angular distance between these peaks allows to judge about the elastic deformation of the intermediate layer. On Shi is ine of the peak from the silicon layer defined by the degree of imperfection of the crystal lattice of the layer.

The results of the declared parameters of the method, in particular the angle of incidence of the x-ray beam to the surface in the study of SNS structures and assessment silicon layer and the intermediate layer are summarized in Tables 1 and 2.

Example 3. In accordance with the claimed method was carried out control of defects and elastic strain in the epitaxial layers of wide bandgap structure of AlGaN/GaN/sapphire layer thickness of AlGaN - 280 a and GaN - 2 μm. The original surface of the sapphire substrate was almost the same crystallographic plane sapphire (0001), misorientation was 0.7°. Epitaxial layers were grown using the MOS-hydride epitaxy (MOCVD). Control, as in examples 1 and 2 was carried out on single-crystal x-ray diffractometer. Analyzed the heterostructure was placed on the object table setup. As the plane reflection sapphire was selected crystallographic plane (112-0). Calculate the angle of incidence of the primary x-ray beam α on the surface of the sample (basal plane (0001)) thus, to obtain a Bragg angle with the plane of the initial growth of GaN layers (112-0) - 8,83°, the center of the detector in this case is installed in position 57° (θ). The program takes into account that the angle of incidence is not Breggovskom angle itself performs the precision computations. Next, similarly to example 1 have radwaste and received interference peaks for layers of GaN and AlGaN (figure 3).

Other examples of implementation of the proposed method are summarized in Tables 1, 2.

Thus. As can be seen from examples (Tables 1 and 2), using the proposed method allows stable enough to assess the presence of transitional (intermediate) layer between the substrate and the epitaxial layer, in some cases, to judge the thickness of this layer, assess its condition, such as the presence of compressive deformation in the layer, to quickly evaluate the structural perfection of epitaxial layers largest width at half-height of the diffraction curves from epitaxial layers.

The effectiveness of the proposed control method in comparison with the prototype, and the analogue is the following:

- sharp to reduce the complexity of the control process from a few hours up to 30-40 minutes.

- the solution of environmental problems through the use of plants with low capacity that does not require work in a specially equipped room;

- reducing the cost of used x-ray machines.

1. The method of control of defects and elastic deformation in the layers of semiconductor heterostructures, including the measurement using x-ray diffractometry using a moving primary x-ray beam with obtaining asymmetric reflections from kristallograficheskih planes, which is the largest angle with the surface of the interface substrate-epitaxial layer, and the definition of strain in the epitaxial layers by changing the distance between the interference maxima from the epitaxial layer and the substrate, characterized in that the use of single crystal x-ray diffractometry with quasi parallel x-ray beam with a total divergence and convergence of the beam 12'-24', get the maximum reflection by azimuthal rotation of the heterostructure around the normal to its surface, and the angle of incidence of the x-ray beam to the surface is in the range of 2.5-9°, then make the adjustment of the Bragg angle by changing the angle of incidence of the primary x-ray beam on the crystallographic plane coincident with the surface of the heterostructure, to obtain maximum reflection and, using the system of crystallographic planes, which showed the growth of epitaxial layers, receive simultaneous reflections from similar systems crystallographic planes of the growing epitaxial layers and substrates, including locking the presence of a transition layer between them.

2. The method of control of defects and elastic deformation in the layers of semiconductor heterostructures according to claim 1, characterized in that to obtain the maximum reflected who I am by azimuthal rotation of the heterostructure around the normal to its surface in the case sirosonic heterostructure AlGaN/GaN Bragg plane enter the direction < 110>.

3. The method of control of defects and elastic deformation in the layers of semiconductor heterostructures according to claim 1, characterized in that to obtain maximum reflection by azimuthal rotation of the heterostructure around the normal to its surface in the case of SNS structures in the Bragg plane enter the direction <331>.