Requirement Document.docx

Requirement Document High Resolution X-ray Diffraction Imaging System

PR NUMBER: 68-1023-20

NRL requires to procure a high resolution x-ray topography system. This system will be used to characterize defects in a variety of materials synthesized at the Electronics Sciences and Technology Division such as GaSb and GeSn based IR materials, SiC, GaN, InP based photovoltaics, perovskites, Ga2O3, and crystalline nanomaterials. The system needs to perform on these materials and will need the following requirements:

1) X-ray source The X-ray source shall be a High Brilliance greater than 300 kW/mm2, and Micro-Focusing Anode type. The anode should be of dual energy construction allowing seamless, automatic switching between Cu and Mo radiation without removing, altering or changing out the x-ray source or any optics.

Basis: In order to perform both reflection mode and transmission mode x-ray topography, it is crucial to have the dual energy configuration. The measurements are expected, in many cases, to be performed for long duration (several hours). Hence, it is vital to be able to switch between Cu and Mo anode via computer control without user intervention. In order to characterize the advanced materials, especially nanomaterials, and superlattices, the high brilliance described above is essential.

2) Goniometer Both the X-ray source and the image detectors shall be mounted on a vertical goniometer for the samples to stay horizontal. The x-ray source, the point and imaging detectors should be able to move such that it is possible to perform both reflection and transmission defect imaging and analysis of the samples. The sample analysis shall be performed with the sample always mounted in a horizontal position for both reflection and transmission measurements, in order to avoid application of external strain. The system shall have the capacity to measure at least a 200 mm diameter wafer edge to edge.

Basis: As explained above the samples need to be mounted horizontally without any clamping method in order to obtain their true inherent crystalline properties. The source and detectors need to be in the diffraction plane and be able to perform both reflection as well as transmission measurements without the need for any user intervention under computer control in order to perform all the necessary measurements for our materials. The 200 mm diameter requirement is essential in performing characterization on SiC wafers for NRL/ONR programs.

3) Optics The instrument shall use multilayer mirrors to produce a parallel beam from the micro-focus spot x-ray source. The system shall have two multilayer mirrors for Cu and Mo radiation. The switching between the Cu and Mo mirrors shall be completed automatically from the instrument control computer.

The instrument must contain the following channel cut crystal monochromaters. These are required for specific diffraction conditions for imaging the materials relevant to NRL/DON needs.

· Si <422>, 2-bounce Monochromator for Cu radiation

· Si <331>, 2-bounce Monochromator for Cu radiation

· Si <220>, 2-bounce Monochromator for Cu radiation

· Si <440>, 2-bounce Monochromator for Mo radiation

Basis: As previously mentioned, measurements lasting several hours shall be conducted using this instrument. It is pertinent that the desired measurements using Cu and Mo sources for reflection and transmission mode geometries be conducted using computer control only to allow for uninterrupted measurements on our samples. The crystal monochromaters listed above are required especially because according to NRL calculations of diffraction conditions, they provide the minimized dispersion with our grown materials. This is required in order to obtain the best resolution images and characterize crystalline perfection of our materials.

4) High Resolution Imaging detectors For imaging of fine X-ray Topography details, the instrument shall have very sensitive and high-resolution imaging detectors described below. The instrument should have the following two imaging detectors mounted permanently on the instrument goniometer, and shall move automatically for each testing conditions without any user intervention. The instrument should be capable of continuous scanning image integration over the entire scanned surface allowing full wafer area mapping without image stitching artifacts

· Imaging detector one should be high sensitivity and have an effective pixel resolution of better than 5.5 microns and effective at both Cu and Mo radiation.

· Imaging detector two should be high resolution and have an effective pixel resolution of better than 2.2 microns and work for both Cu and Mo radiation.

Basis: According to the NRL calculations we expect dispersion in many of our crystalline materials as low as 2E-7 with the correct crystal monochromater as described in Sec. 3. This low dispersion will allow us to observe crystalline defects and imperfections that are highly resolved, however, only with a higher resolution imaging detector (better than 2.2 mirons). The requirement for lower resolution, high sensitivity detector is for performing measurements over larger areas with faster throughput since the higher resolution detector has smaller field of view.

5) Analysis Techniques and Software

· Instrument shall be capable of X-Y scanning a sample edge to edge an up to 200mm wafer.

· Instrument shall be capable of performing wafer curvature correction using scanned rocking curve analysis in order to provide even x-ray illumination for defect analysis.

· Dislocation analysis of substrate wafers shall include dislocation type delineation and dislocations density per unit area over entire scanned wafer.

· The instrument shall have the capability of X-ray Section Topography that will be able to reconstruct a 3-D image of the dislocation strain field within a substrate sample.

Basis: The analysis software is required to interpret the results seamlessly from the acquired data. The amount of data acquired is expected to be several gigabytes. Software automation is essential in order to process the data into useful quantitative metrics to meet our program goals. Section topography is an essential technique in order to investigate how defects evolve over the course of growth of our materials. This will enable us to mitigate defects and crystalline imperfections in the growth/synthesis of our materials.

I certify that the facts and representations made in and which form a basis for this justification are accurate and complete.