US3833810A

US3833810A - Method of x-ray diffraction topography of monocrystals and apparatus for effecting same

Info

Publication number: US3833810A
Application number: US00326335A
Authority: US
Inventors: N Komyak; V Ljuttsau; V Efanov; N Rabodzei
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-01-28
Filing date: 1973-01-24
Publication date: 1974-09-03
Anticipated expiration: 1991-09-03
Also published as: AT346629B; FR2169617A5; NL7301024A; GB1414572A; CS176429B1; DD103727A1; DE2304119A1; DE2304119B2; HU166083B; ATA38073A

Abstract

A method of X-ray diffraction topography of monocrystals, consisting in irradiation of every point of an investigated area of the cross-section of a monocrystal by X-rays and separation of the radiation diffracted at a specific angle from said every point of the investigated area of the cross-section of the monocrystal, simultaneously for all these points of the investigated area. An apparatus for X-ray diffraction topography of monocrystals, realizing the above method, comprising a source of X-rays and an investigated monocrystal, a collimator, a radiation detector and a means for recording the topogram of the monocrystal, positioned successively in the path of the Xradiation. The collimator, of which the direction of collimation is oriented at a specified orientation angle in relation to the crystallographic axes of the monocrystal, is in the form of a two-dimensional matrix of parallel capillaries.

Description

United States Patent 1 Efanov et al.

[ Sept. 3, 1974 METHOD OF X-RAY DlFFRACTlON TOPOGRAPHY OF MONOCRYSTALS AND APPARATUS FOR EFFECTING SAME [76] Inventors: Valery Pavlovich Efanov, ulitsa Profsojuznaya, 96, kv. 192, Moscow; Nikolai lvanovich Komyak, Kostromskoi prospekt, 22, kv. 71, Leningrad; Vsevolod Grigorievich Ljuttsau, ulitsa Garibaldi, 19, korpus l, kv. 49, Moscow; Nikolai Vasilievich Rabodzei, ulitsa Institutskaya, 6a, kv. 39, Fryazino Moskovskaya oblasti, all of USSR.

[22] Filed: Jan. 24, 1973 [21] Appl. No.: 326,335

[30] Foreign Application Priority Data Jan. 28, 1972 U.S.S.R 1743310 Jan. 28, 1972 U.S.S.R .1 1747007 [52] US. Cl. 250/273, 250/274 [51] Int. Cl. G0ln 23/20 [58] Field of Search 250/272, 273, 274, 275, 250/276 [56] References Cited UNITED STATES PATENTS 2,549,987 4/1951 Parrish 250/272 Primary ExaminerJames W. Lawrence Assistant Examiner-C. E. Church Attorney, Agent, or Firm-Holman & Stern [5 7 ABSTRACT A method of X-ray diffraction topography of monocrystals, consisting in irradiation of every point of an investigated area of the cross-section of a monocrystal by X-rays and separation of the radiation diffracted at a specific angle from said every point of the investigated area of the cross-section of the monocrystal, simultaneously for all these points of the investigated area. An apparatus for X-ray diffraction topography of monocrystals, realizing the above method, comprising a source of X-rays and an investigated monocrystal, a collimator, a radiation detector and a means for recording the topogram of the monocrystal, positioned successively in the path of the X-radiation. The collimator, of which the direction of collimation is oriented at a specified orientation angle in relation to the crystallographic axes of the monocrystal, is in the form of a two-dimensional matrix of parallel capillaries.

3 Claims, 2 Drawing Figures PATENTED 3 974 SHEET 10F 2 PATENTEU SEP 3 74 SHEET 20F 2 METHOD OF X-RAY DIFFRACTION TOPOGRAPHY OF MONOCRYSTALS AND APPARATUS FOR EFFECTING SAME BACKGROUND OF THE INVENTION The invention relates generally to methods of detection of flaws in the crystalline structure of solids and to apparatus for effecting same, and more particularly, it relates to methods of X-ray diffraction topography of monocrystals and to apparatus for effecting same.

There are known methods of X-ray diffraction topography of monocrystals, wherein all the points of an investigated area of the cross-section of a monocrystal are irradiated by X-rays, whereafter the radiation diffracted at a specified angle from all the points of the investigated area of the cross-section of the monocrystal is separated, and the topogram of the monocrystal is obtained.

In these known methods, the recording of the topographic images of all the points of the investigated area of the crosssection of a monocrystal is effected either by obtaining the complete diffraction image of a given point (e.g., with the use of a photographic film), separating only the diffracted radiation corresponding to a specified angle (or to deflection from the angle), or else by setting the receiving slot (e. g., that of a scintillation detector) directly to a position corresponding to this specified angle and by transmitting the electric signal produced by this detector to a recording device to register the information representing the state of the monocrystal at this given point of the cross-section thereof.

When passing from one given point to another, there is shifted either the photographic film, to produce the complete diffraction image of this other point, or else the cording device, so that the latter will register in this new position the information representative of the flaws of the crystalline structure of the monocrystal in this other point.

Apparatus for X-ray diffraction topography of monocrystals, are also known in the art realizing the above known methods.

In these known apparatus, the radiation from a source of X-rays is diffracted on a monocrystal being investigated, whereafter this diffracted radiation is made to pass through a collimator of which the direction of collimation is oriented at a specified orientation angle in relation to the crystallographic axes or the reticular planes of this monocrystal and to fall on a radiation detector and a device for recording the topogram of the monocrystal.

In these known apparatus, the source of X-rays is in the form of an X-ray tube producing either a narrow beam of X-rays, or else a beam which is subsequently collimated, while the collimator, oriented at a specified angle in relation to the crystallographic axes of the investigated monocrystal, is in the form of a single channel which, more often than not, is the receiving slot of the detector, oriented at a specified angle in relation to the axes of the monocrystal.

When these known apparatus are operated, the investigated monocrystal and the recording device are synchronoulsy displaced relative to the X-ray beam that is fixed in space, whereby the recording device registers unambiguously the intensity of the radiation transduced by the detector, as a function of the position of the monocrystal in respect of the beam of X- rays falling thereupon.

A disadvantage of the above described known apparatus realizing the known methods is the necessity of ensuring high-precision adjustment of the system, as well as high-precision mechanical displacement of the monocrystal, accurately synchronized with the accompanying displacement of the recording means.

Among the short comings of the complicated process of topography effected by these known appartus realizing the known methods are the relatively slow rate of the investigation as well as the impossibility of subjecting the investigated monocrystal to any additional action directly in the process of topography.

SUMMARY OF THE INVENTION It is an object of the present invention to develop a method of X-ray diffraction topography of monocrystals, which will provide for speeding up the process of obtaining topograms of monocrystals.

Another object of the present invention is to develop a method of X-ray diffraction topography of monocrystals, which will also provide for investigating the dynamics of origination and development of flaws in the crystalline structure of monocrystals.

Still another object of the present invention is to provide an apparatus for X-ray diffraction topography of monocrystals, realizing the above method.

A further object of the present invention is to provide an apparatus for X-ray diffraction topography of monocrystals, which will provide for elimination of any mechanical displacement of the units of the apparatus in the process of topography.

These and other objects are attained in a method of X-ray diffraction topography of monocrystals, consisting in irradiation of every point of an investigated area of the cross-section of a monocrsystal by X-rays, separation of the radiation diffracted at a specified angle from every said point of the investigated area of the cross-section of the monocrystal and obtaining the topogram of the monocrystal, in which method, in accordance with the present invention, the separation of the radiation diffracted at a specified angle from every the point of the investigated area of the cross-section of the monocrystal is effected simultaneously for every the point of the investigated area.

In an apparatus for realizing the herein disclosed method of X-ray diffraction topography of monocrystals, wherein the radiation from a source of X-rays is diffracted on a monocrystal, whereafter the diffracted radiation is made to pass through the main collimator of which the direction of collimation is oriented at a specified angle in relation to the crystallographic axes of the monocrystal and to fall upon thhe radiation detector to be registered by a recording means, in accordance with the present invention, the main collimator includes a two-dimensional matrix of parallel capillarres.

It is advisable that the apparatus include an auxiliary collimator positioned upstream of the monocrystal in the direction of the X-radiation, the direction of collimation of the auxiliary collimator being oriented at an angle in relation to the crystallographic axes of the monocrystal, which is equal to the angle of orientation of the main collimator, so that the X-radiation that has passed through the auxiliary collimator will also pass,

after having been diffracted on the monocrystal, through the main collimator.

Due to such an embodiment of the herein disclosed apparatus for X-ray diffraction topography of monocrystals, realizing the herein disclosed method, the distance between the source of X-rays and the radiation detector can be reduced to 2.0 mm to 10.0 mm, which results in a substantial reduction of the time of obtaining a topogram.

Furthermore, the herein disclosed apparatus realizing the herein disclosed method, due to the separation of the radiation diffracted at a specified angle from every point of the investigated area of the cross-section of the monocrystal simultaneously for all the points, as well as to the reduced time of topography, makes it possible to investigate the dynamics of origination and development of various flaws in the crystalline structure of monocrystals, directly in the process of manu facture of various semiconductor devices (p-n junctions, integral circuits incorporating monocrystals).

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be further described in connection with an embodiment thereof, with referece being had to the appended drawings, wherein:

FIG. 1 is a schematic view of an apparatus for X-ray diffraction topography of monocrystals, realizing the herein disclosed method; and

FIG. 2 is an enlarged perspective view of portion A of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in particular to the appended drawings, the apparatus for realizing the method of diffraction topography of monocrystals in accordance with the present invention, comprises a source 1 (FIG. 1) of X-rays and the following units positioned along the path of the radiation coming from this source 1: a collimator 2, an investigated monocrystal 3 (silicon) in the form of a flat-parallel plate possessing pre-established crystallographic characteristics (syngony, lattice spacing, orientation of the crystallographic or reticular planes in relation to the face planes), at collimator 4, a detector 5 and a means 6 for recording the topogram of the monocrystal 3.

The collimator 4 is the main collimator of which the direction of collimation is oriented at a specified orientation angle (which is the Bragg angle 6) in relation to the crystallographic axes of the monocrystal 3. The. collimator 4 is in the form of a two-dimensional matrix made up by a system of parallel capillary tubes 7 (FIG. 2), the diameter of these capillary tubes being approximately microns.

However, in an apparatus embodying the present invention, the main collimator may be in the form of a two-dimensional matrix made up by a system of parallel capillaries of any suitable shape and size.

The collimator 2 is the auxiliary collimator which has a structure similar to that of the main collimator 4, i.e, it is a two-dimensional matrix including a system of parallel capillaries 8, the direction of collimation of this auxiliary collimator 2 being oriented at an orientation angle in relation to the crystallographic planes of the monocrystal 3, which is equal to the orientation angle of the main collimator 4, whereby the X-radiation that has passed through this auxiliary collimator 2 is made to pass, after having been diffracted on the monocrystal 3, through the main collimator 4.

However, the structure of the auxiliary collimator may be different from that of the main collimator, as far as both the shape and the arrangement of the capillaries of the matrix are concerned.

It is possible to embody an apparatus realizing the method according to the present invention, having only the main collimator. However, in this embodiment, the contrast of the topogram on the detector is not as good.

The source 1 of X-rays in the presently described embodiment is in the form of a high-voltage cathode ray tube incorporating a target anode 9 which is a coating on the beryllium outlet window 10, a cathode l1 and a deflection system 12, electrically connected to a power unit 13 including a scanning control system.

The detector 5 in the presently described embodiment is in the form of a target of an X-ray responsive television-type transmitting tube 14 incorporating a cathode l5 and a deflection system 16, electrically connected to a power unit 17 including a scanning control system.

The means 6 for recording the topogram of the monocrystal 3 is in the form of a television-type receiving cathode ray tube electrically connected to the transmitting tube 14.

However, an apparatus realizing the herein disclosed method of X-ray diffraction topography of monocrystals may employ any other known kind of radiation detector (photographic film included) capable of an unambiguous registration of the position of a point on a plane and of the intensity of the radiation corresponding to this point. If a photographic film is employed as the radiation detector, it would then serve both as the detector and the means for recording the topogram of a monocrystal.

The herein disclosed apparatus further incorporates a means (not shown) for fixing in place the source 1 of X-rays, the monocrystal 3, the collimators 2 and 4 and the detector 5, proving for the adjustment of the respective positions of the above-listed components and ensuring rigid fixation thereof in the course of production of a topogram.

The operation of the herein disclosed apparatus for X-ray diffraction topography of monocrystals, realizing the method in accordance with the invention, is as follows.

When a negative potential of 10 to 40 kV is applied to the cathode 11 (FIG. 1) of the cathode ray tube 1 (the target anode 9 of the tube being grounded), there is produced, across the target anode 9, an X-radiation 18 which issues in the form of a wide cone.

The collimator 2 selects from this cone 18 of X-rays only that direction 19 of radiation which is directed at the Bragg angle 0 in relation to the selected system of the reticular planes of the monocrystal 3 being investigated.

However, if the auxiliary collimator is omitted from the structure of the apparatus, the monocrystal itself would select the required direction from the cone of the X-rays, but then the signal-to-noise ratio at the detector would not be as good.

As a result of the diffraction of the X-rays on the investigated area of the cross-section of the monocrystal 3, there emerges from the latter monochromatic radiation originated by the material of the target anode 9 as a beam 20 of parallel rays, oriented in a direction depending on the Bragg angle 6 for the given type of the monocrystal 3 as a whole and also weakened dissipated radiation (not shown). The radiation passes through the capillaries 7 of the collimator 4, whereby the radiation diffracted at a specified angel (the Bragg angle is separated in the form of the above-mentioned beam 20 of parallel X-rays from every point of the investigated area of the cross-section of the monocrystal 3, simultaneously for every point of this investigated area. This beam 20 of parallel X-rays falls upon the detector in the form of an image of the topogram of the crosssectional structure of the investigated area of the monocrystal 3. The detector 5 transmits this image of the topogram to the recording device 6, i.e. to the television-type receiving tube.

The dissipated radiation and the radiation diffracted at other angles is substantially weakened by the material of the collimator 4.

If, in the course of initial positioning of the components, the angle between the selected system of the crystallographic (reticular) planes of the the monocrystal 3 and the direction of collimation of the collimator 4 is not equal to the Bragg angle, the monocrystal 3 is coarsely angularly adjusted, until an image appears on the screen of the receiving television-type tube, in which position the monocrystal 3 is retained. The same result can be obtained by rotation of the collimator 4. Thereafter the collimator 2 is introduced to step up the contrast of the image.

If a series of monocrystals of a single type is to be investigated, the collimators 2 and 4 are so selected, that the angle between the face planes of the monocrystal 3 and the direction of collimation of the collimators 2 and 4 are equal to the Bragg angle for this type of monocrystals. In this case, the relative positioning of the collimators 2 and 4 is adjusted but once and retained throughout the entire series of investigations. In this way, relative positioning and adjustment of the collimators 2 and 4 and the monocrystal 3 is substantially simplified. When monocrystals of a different type are to be investigated, the whole collimator assembly is replaced.

While the primary electron beam approximately microns in diameter scans the target anode 5, a corresponding beam of X-rays successively traverses the investigated monocrystal 3. In each point of the investigated area, provided that the Bragg condition for the monocrystal as a whole is observed therein, there takes place diffraction of the incident beam, and the diffracted beam, after having passed through the collimator 4, is received by the detector 5.

Irradiation by X-rays of the entire cross-sectional area of the monocrystal may be effected simultaneously as well, and this would not constitute any departure from the scope of the present invention, but involve the incorporation of a source of X-rays which is at present unprofitable from the point of view of its specific power output; on the other hand, the incorporation of the source of X-rays with a scanning beam is preferable becuase with the same power consumption its capacity is greater by 3 to 4 orders of magnitude.

All the components of the herein disclosed apparatus being rigidly fixed throughout the process of obtaining a topogram of the monocrystal 3, there is offered a principally new possibility of repeating a series of investigations of the same rigidly fixed monocrystal 3 subjected to various kinds of external action, e.g., mechanical, thermal, etc.

The herein disclosed apparatus realizing the method in accordance with the present invention may be successfully employed for control of the quality of monocrystals, as part of production of various semiconductor and laser devices. Due to speedy obtainment of a topogram and to the simplisity in operation and maintenace, the herein disclosed apparatus may be employed, for instance, for mass control of monocrystals in the manufacture of integral circuits.

Furthermore, the apparatus realizing the herein disclosed method may be employed in scientific research, since it enables the investigation of the dynamics of the development of various flaws in the crystalline structure of monocrystals in the course of their growth, as well as those resulting from an external action.

What is claimed is:

1. A method of X-ray diffraction topography of monocrystals, comprising the steps of: irradiating every point of an investigated area of the cross-section of a monocrystal by X-rays; separating the radiation diffracted at a specified angle from every point of the investigated area of the cross-section of the monocrystal simultaneously for all the points of the investigated area from the radiation diffracted at all other angles; and providing a topogram of the monocrystal.

2. An apparatus for X-ray diffraction topography of monocrystals, said apparatus comprising: a source of x-rays; an investigated monocrystal positioned behind said source of X-rays in the path of the radiation issuing therefrom so that said radiation is diffracted by said monocrystal; a main collimator positioned behind said investigated monocrystal in the path of said defracted X-radiation being formed as a two-dimensional matrix of parallel capillaries the direction of collimation of said main collimator being oriented at a given angle to the crystallographic axes of said investigated monocrystal and through which the radiation diffracted at the given angle to the crystallographic axes of said investigated monocrystal passes from each point of the cross-section of said investigated monocrystal with the exclusion of radiation diffracted at all other angles; a detector positioned behind said main collimator in the path of said diffracted X-radiation so that said diffracted X-radiation falls on said detector; and means for recording topogram of said monocrystal, said recording means positioned behind said detector in the path of said diffracted X-radiation.

3. An apparatus as claimed in claim 2, further comprising an auxiliary collimator positioned in front of said investigated monocrystal in the path of said X- radiation, the direction of collimation of said auxiliary collimator being oriented at an orientation angle in relation to said crystallographic axes of said investigated monocrystal which is equal to said orientation angle of said main collimator so that said X-radiation passing through said auxiliary collimator is made to pass, after having been diffracted on said monocrystal, through said main collimator.

Claims

1. A method of X-ray diffraction topography of monocrystals, comprising the steps of: irradiating every point of an investigated area of the cross-section of a monocrystal by Xrays; separating the radiation diffracted at a specified angle from every point of the investigated area of the cross-section of the monocrystal simultaneously for all the points of the investigated area from the radiation diffracted at all other angles; and providing a topogram of the monocrystal.

2. An apparatus for X-ray diffraction topography of monocrystals, said apparatus comprising: a source of x-rays; an investigated monocrystal positioned behind said source of X-rays in the path of the radiaTion issuing therefrom - so that said radiation is diffracted by said monocrystal; a main collimator positioned behind said investigated monocrystal in the path of said defracted X-radiation being formed as a two-dimensional matrix of parallel capillaries the direction of collimation of said main collimator being oriented at a given angle to the crystallographic axes of said investigated monocrystal and through which the radiation diffracted at the given angle to the crystallographic axes of said investigated monocrystal passes from each point of the cross-section of said investigated monocrystal with the exclusion of radiation diffracted at all other angles; a detector positioned behind said main collimator in the path of said diffracted X-radiation so that said diffracted X-radiation falls on said detector; and means for recording topogram of said monocrystal, said recording means positioned behind said detector in the path of said diffracted X-radiation.

3. An apparatus as claimed in claim 2, further comprising an auxiliary collimator positioned in front of said investigated monocrystal in the path of said X-radiation, the direction of collimation of said auxiliary collimator being oriented at an orientation angle in relation to said crystallographic axes of said investigated monocrystal which is equal to said orientation angle of said main collimator so that said X-radiation passing through said auxiliary collimator is made to pass, after having been diffracted on said monocrystal, through said main collimator.