DE1901666A1 - Procedure for crystal topography and apparatus for performing this procedure - Google Patents

Description

Dipl.-Ing. Dipl. Oec pobt DIETRICH ί SWINSKY

PATENT ADVERTISEMENT " _Iftn " RO.

8 Münden 21 - Goüfconür. 81 »* ™ ' ^13b *

^Telephone ^ ¹⁷ ' ² , 5454-11 / He ₀

Compagnie Francaise Thomson Houston-Hotchkiss Brandt Paris 8, Boulevard Hauasmann _; 173, France

"Procedure for crystal topography and device for Implementation of this procedure "

French priority of January 19th 1968 from the French patent application Mr ₀ 136 735 (Seine)

The invention concerns a crystal topography method and ter use of an X-ray tube with a straight radiator and a crystal piece arranged on a rotatable support -kes and an linigem spotlight is located, with a piece of crystal support, which is alignable around a vertical and horizontal axis, and a support for photographic plates.

The crystal topography is determined by the refraction of X-ray beams len and is used to generate images on which one can see slight errors in the stacking of crystal units, such as the can observe defects known as mosaic structure in relatively large blocks.

Numerous topography methods using X-rays are already known. Still, most need either mechanical

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accurate and difficult to manufacture devices (for "B _e by the method of Lang), or an unusual position of the straight radiator of a conventional tube opposite the angle axis (z ₀ B ₀ by the methods of Berg-Barret and Borrmann) or the use of a tube with point-shaped radiator »

The invention has for its object to provide a method of the type mentioned, in which a conventional tube with a straight radiator in the normal position, i.e., "h _e is used in parallel to the axis of the goniometer, without it / is Noty Endig, the usual To change the goniometer of an X-ray spectrometer or to add auxiliary mechanisms to this goniometer. The invention is also intended to create the aforementioned device for carrying out the method, which has a very simple and economical structure, especially in industrial laboratories that are not specialized in radio-crystallography can be, however, by the analysis of large single crystals, beispiels-vra.se in the manufacture of semiconductor, piezoelectric or acoustic-electrical components is possible _o the above object is solved by the method proposed here primarily the fact that according to the invention the straight one Radiator of the X-ray tube is arranged vertically, that furthermore a vertical gap limiting the divegence of the rays to the size of the crystal piece and then a thin horizontal gap with a thickness of about 10 to 30 microns is arranged between the X-ray tube and the rectilinear radiator, da3 furthermore the crystal piece is aligned on the one hand about a horizontal axis in order to set a group of lattice planes of the crystal piece in a vertical position, and on the other hand about a vertical axis so that the X-rays reach a point

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reach of the crystal piece under Bragg ¹ schem incidence, that furthermore a photographic plate close to the crystal piece on either side of the beam invasion, when a product obtained by .Reflexion image is desired, or is arranged on the opposite side when a lun by through-beam ^ obtained image is desirable and that finally, without moving the x-ray or the photographic plate, the crystal piece is rotated about its Yertical axis by an angle which is limited to the size that is necessary for all irradiated points of the crystal piece in succession Bragg ¹ see idea arrive «,

An advantageous embodiment of the method according to the invention consists in that a group of lattice planes is selected for which the X-rays which are ^{refracted by selective Bragg 1} reflection have a direction adjacent to the normal direction on the crystal piece.

Another advantageous embodiment of the invention The method consists in the fact that the rotational movement of the crystal piece about a vertical axis is a rotational movement with alternating Direction, limited amplitude and constant velocity is »

The device for carrying out the method according to the invention consists in that a fixed tubular eyepiece located between the X-ray tube and the crystal piece contains the vertical slit and the horizontal slit that furthermore serves to limit the divergence of the X-rays the perpendicular gap provided for the size of the crystal piece is directed towards the X-ray tube and that finally the crystal « piece carrier has a mechanism that the Kristailstück the rotary motion is given in alternating directions with limited amplitude and constant speed.

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In the method according to the invention, an X-ray beam is projected onto the crystal piece to be examined and the crystal piece is aligned in such a way that, on the one hand, a group of crystallographic planes of the crystal piece is perpendicular and, on the other hand, the X-rays reach an area of the crystal piece under Bragg incidence was a photographic plate in the vicinity of the crystal piece either before this, if you want to work with reflection, or behind this, if you will work with irradiation "Then there is the photographic plate and the X-ray solid-standing _e is allowed the crystal piece Rotate about a vertical axis so that one after the other Bragg's incidence is obtained at all points of the crystal which are irradiated by the X-ray beam. The crystal piece can either be rotated slowly or with a sequence of oscillations Total duration equal to the required exposure time is «,

The best results are obtained when the following measures are taken:

Use of an X-ray tube with a straight vertical radiator and passage of the beam of this tube through a vertical slit, the divergence to the useful width of the crystal «, limited piece, and then through a thin horizontal gap with a thickness of preferably about 10 to 30 microns,

Select the group of planes so that the piece of crystal is little opposite is inclined to the central direction of the beam,

Using a group of planes for which the refracted ray is as close as possible to the normal on the piece of crystal.

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Other features and advantages obtained by them from the description or the drawings in which the invention are light \ modern method and, for example, selected embodiment of the device schematically illus- · "Is show:

Pig # 1 the scheme of a radiocrystalllographic arrangement, which enables the method according to the invention to be carried out, and

Pig · 2 is a simplified perspective view of a Implementation of the device specific to the method according to the invention,

In Fig. _# 1 the rectilinear radiator I ^ of a Honing tube and a piece of crystal E are shown, between which a vertical gap E ^ and a horizontal gap F- are arranged. The radiator P ₁ is in a vertical position, the vertical gap P ₂ limits the divergence of the X-rays to the utilized part of the crystal piece E. The horizontal gap F ₅ is thin. Thus, the crystal piece E can be irradiated on its entire surface with X-rays which, after having crossed the horizontal gap F, form a beam D. Axis VV in the direction of the arrow 1 and on the other hand to rotate about a horizontal axis in the direction of the arrow 2. A photographic plate or surface P is arranged in a row on the crystal piece and lies roughly parallel to the radiation surface (the surface through which the X-rays irradiate the crystal piece E) *

¹ According to the invention, the position of the crystal piece E is set, indtm it in the direction of the arrows 1 and 2 in such a way

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is rotated so that a group of lattice planes h, k _s 1, is perpendicular and aligned with the source of the X-rays. Because of the angular opening a of the beam, the X-rays do not have the same incidence on the entire irradiated surface of the crystal piece "Only a small part of the planes h, k, 1 can be in the position of selective Bragg ¹ see reflection". The area in question is an arc with a very large radius of curvature, the image of which is created on the photographic plate (P) ₀ line slight rotation of the crystal piece E around the vertical axis YV in the direction of the arrow 1 leads to another small group of lattice planes h | k, l, into the Bragg's position ₀ This results in an image of this new area on the photographic plate P next to the previous image if there has been no change in the position of the photographic plate P or in the alignment of the X-ray beam rotated alone in order to successively lead the points of the crystal piece into the Bragg ¹ see position that of the X-ray The photographic plate P then stores a sequence of images which together form a band that is blackened perfectly evenly. However, such a band of uniform color can only be obtained if the structure of the crystal piece is regular. In those cases, the band will be marked with light spots in which planes h, k, I _{1 of} the selected group are missing or poorly aligned, since the selective Bragg'sGhe reflection does not occur or occurs at an inappropriate time. The method according to the invention therefore enables the creation of the topography of the crystal piece I,

It can be seen from FIG. 1 that the angle of incidence of the X-rays is equal to i with respect to an edge of the crystal piece E and equal to i + a opposite the other edge of the crystal piece iste where a is the opening angle of the bundle of rays D.

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Assuming that the angle i is equal to the Bragg's angle is, it is sufficient to rotate the crystal piece by an angle α about the vertical axis V-V in the direction of the arrow 1, so that all of the irradiated points of the piece of crystal succeeded one after the other in the Bragg's position * A rotation is very common by a few degrees sufficient - to get a complete picture

Us it should be noted that the image obtained is somewhat deformed, because it is a projection starting from I ^ in the horizontal plane and from F., in the vertical plane _e It is easy to calculate the enlargement ratio along these axes E, F., of 250 mm and E, F * of 125 mm with a plate of 10 mm of the crystal piece you get:

Horizontal _{magnification G H} = 260/250 = 1.04 Vertical magnification G ^ = 135/125 = 1.08.

The ratio & y / & - u = 1 »04. As a result, the magnification deviation is only 4 $. Therefore, in the most common cases, the deformation of the image is of no importance.

The image can be obtained by rotating the crystal piece through an angle α in a time equal to that required Exposure time is. However, a better picture is generally obtained by holding the piece of crystal during the duration of this exposure time can oscillate. The exposure time is relatively short with normal emulsions. She lies in the order of an hour.

The photographic plate P can be both close to the radiation-emitting surface (as in Figure _# 1) as a "be arranged close to the irradiated surface will in the first instance by By"

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radiation and exposed in the second pail by reflection «

It is desirable that the horizontal gap F 1 be thin, for example on the order of 10 microns, _{or the like}

In any case, it is desirable to meet the following conditions:

The plane group h, k _f 1 · to be chosen in such a way that the plane of the crystal piece is slightly differing from the central "direction of the beam D in order to use the useful divergence limits; a plane h, k, 1, in which the refracted Beam is as close as possible to the normal on the crystal piece in order to avoid or at least reduce distortion.

These conditions are sufficiently met in the case of a silicon wafer 111 through levels 311, 400 and 331 if you are working with irradiation, and through levels 511, 440, 531 and 620, when working with reflection «For example, the case of plane 311 is most unfavorable for transmission. for which the angle of incidence of the X-rays is 30 ° 47 'and the angle of reflection of the refracted rays is 86 ° 57 * » In this case, an oscillation of + 1 ° is sufficient to examine a 20 mm diameter plate that is 250 mm from the Emitter is located away “The resolution can be 10 microns be*

The method according to the invention is used successfully to remove defects in crystals, in particular in corundum single crystals determine, as well as for an investigation with the influence of diffusions on the properties of integrated

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Circuits: i * ntersu.cht is «

The method according to the invention therefore has a safe one Effectiveness on »Its original advantage consists in the Simplicity of the files necessary for its implementation «The procedure can be carried out with a conventional spectrometer

be performed using an X-ray tube and a norma—. les goniometer is used. The formation of the X-rays takes place with "readily available work equipment» It is sufficient to give the KristaHLstüek a simple rotary movement around a vertical * axis _# without the need to move other elements such as the photographic plate or the beam »This process is therefore much simpler than the previously known methods, for which the adjustment of the beam is very difficult or for which, for example, expensive and complicated additional mechanisms have to be provided in order to bring about simultaneous linear movements of the crystal piece and the photographic plate Method of obtaining a satisfactory image with a relatively short exposure time «

One embodiment of the device for carrying out the method according to the invention is in lig. 2 “This device does not require the expensive equipment with which the radiocrystallographic laboratories are equipped. This device essentially comprises a rotating block 3 # on which the crystal piece E ^{- is} arranged, and an eyepiece 4, one opening of which is located on the crystal piece. X-ray tube of a conventional spring with a linear vertical radiator can be glued,

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The rotatable block 3 and the eyepiece 4 to be of a table 5 geahlten "The eyepiece 4 is connected to the table 5 by a foot 6 * The tube of the eyepiece 4 contains 2 column F ₂ and F _3, which are respectively vertical and horizontal and fulfill the same functions as the columns denoted by the same reference numerals in FIG. The vertical gap F ₂ is arranged at the end of the eyepiece which is directed towards the X-ray tube. The horizontal gap F ₃ is located approximately in the middle between the gap F ₃ and the crystal piece E _0. The gap F ₂ serves to open the opening to limit the X-rays in the horizontal direction «The gap F ₃ is used to reduce the beam to the size of a thin bundle» Preferably the gap F _{3 has} a width between about 10 and 30 microns «

The rotatable block 3 comprises a circular plate 7 having a vertical axis, which is arranged on the table 5 so that it can rotate about its axis, for example by means of a not shown in the drawing, ball bearing ring _β The plate 7 carries the crystal piece carrier 8, a mechanism 9, in order to produce an alternating rotational movement of the crystal piece carrier around its vertical axis, a pivotable plate carrier 10 and a holding arm 11 for a counter tube, not shown. The vertical axis of the plate 7 and that of the crystal piece carrier 8 practically coincide and almost touch the crystal piece E. The holding arm 11 is arranged behind the crystal piece carrier 8. The plate carrier 10 can be pivoted in order either to arrange it between the crystal piece carrier and the holding arm or to put it in the retracted position.

On the crystal piece carrier 8 is a crown system with an endless screw provided so that the piece of crystal can be rotated around a horizontal axis, around a selected group of the guitar

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"This setting is usually made by taking the readings from the counter located on the holding arm 11 as a basis". The plate exciter is in the retracted position. the plate 7 is allowed to rotate and the crystal piece is also rotated about the vertical axis in order to place at least one plane h, k, 1, of the crystal piece in the Bragg ¹ position opposite the incident X-rays. It should be noted that this alignment can be determined beforehand with a good approximation by calculation. The mechanism 9 must generate an oscillating movement at a constant speed of the crystal piece carrier around the vertical axis. This mechanism is represented in a simplified form, for example, by a system that includes a toothed sector which is operated by a motor (not shown) with two gear directions and the movement of which is limited by stops with electrical contacts that determine the gear direction reverse the motor.

The apparatus shown in Fig. 2 does not include a heavy one piece to be produced and can therefore be constructed without great effort. It is completely sufficient for the execution of the method according to the invention, because it has the necessary gene elements to the X-ray of a conventional outer tube. re to shape, as well as elements that make it possible to rotate the piece of crystal in a suitable shape around a vertical axis. hen. It should be noted that this very simple movement of the piece of crystal is the only movement involved in the invention. appropriate procedure takes place. Mainly this feature is responsible for the low price of the in Fig. 2 device shown. This device can be of great service in the control laboratories leading to the manufacturing workshops electronic components and have to carry out controls on single crystals, but their actuation does not

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the acquisition of the complicated and expensive material which is commonly used in radiocrystallography *

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Claims (1)

Dipl.-Ing. Dip !, oee. puM. DIETRICH IFWINSKY Λ $ ftk PATENT ADVOCATE " ^Γ * Möechen 21 - Goithonfstr. H _, _, _ττΛΐ Oompagnie Francaise Thomson Houston - Hotchkiss Brandt Paris 8, Boulevard Haussmann 173, France Patent claims; , Crystal topography method using an X-ray tube with a rectilinear emitter and a piece of crystal arranged on a rotatable support, characterized in that the rectilinear emitter (F ..) of the X-ray tube is arranged vertically, that furthermore between the X-ray tube and the rectilinear emitter (P ₁ ) the divergence of the rays on the size of the crystal piece limiting vertical gap (F ₂ ) ^and then a thin horizontal gap (i *) with a thickness of about 10 to 30 microns is arranged, that also the crystal piece (E) on the one hand around a horizontal axis in order to set a group of lattice planes (h, k, 1) of the crystal piece in a vertical position, and on the other hand around a vertical axis (V) so that the X-rays under a point of the crystal piece Bragg ¹ see »the incident, that a photographic plate (P) continues to be close to the crystal piece either on the side of the ray incidence ■ if, when an image obtained by reflection is desired or on the opposite side if a radiographic image is desired is, and that after all without the X-ray or the w 2 · ■ · PRüP 4 414 909836/1276 4901666 Before moving the plate (Ρ) the piece of crystal is rotated around its vertical axis by an angle which is limited to the size necessary for all of the irradiated points of the piece of crystal (E) to be placed one after the other in Bragg ¹ see idea arrive «, 2ο The method according to claim 1, characterized in that cLbB a group of lattice planes (h, k, 1) is selected for which the X-rays ^{refracted by selective Bra ^ g f} cal reflection, a direction adjacent to the normal on the crystal piece to have", 3. Method according to claim 1 or 2, characterized in that that the rotary movement of the crystal piece (E) around the vertical axis (V) is a rotary movement with alternating sighting, limited amplitude and constant speed is «, 4 »Device for performing the method according to one of the preceding claims, which is located in front of an X-ray tube with a vertically arranged rectilinear radiator,. with a crystal piece carrier which can be aligned about vertical and horizontal axes, and a carrier for photographic plates, characterized in that a fixed tubular eyepiece (4) located between the X-ray tube and the crystal tuck (S) clears the vertical gap ( E ₂ ) and contains the horizontal gap, that furthermore the perpendicular gap provided to limit the divergence of the X-rays to the size of the crystal piece (E) is directed towards the X-ray tube and that finally the crystal piece carrier (7) has a mechanism (9) that allows the Crystal piece (E) gave the rotary movement in alternating directions with limited amplitude and constant speed BATH ORIGINAL 909836/1276