DD227559A1 - METHOD FOR THE PRODUCTION OF GETTING-RICH SILICON DISCS - Google Patents

Abstract

The aim of the invention is to increase the yield and reliability of microelectronic components by using powdery and dimensionally stable silicon wafers. The object of the invention to provide a method for producing slices with permanent and uniform getter effect in suppressing disc distortion is achieved by providing slices selected with respect to their surface shape with an adapted, concentric, scribe-like mechanical disturbance whose intensity and surface density are varied can. Subsequently, the disturbed Scheibenoberflaeche is provided with a cover layer for stabilization.

Description

Field of application of the invention

The invention relates to a method for producing getterfähiger silicon wafers, which represent a prerequisite for the production of high-quality, in particular highly integrated microelectronic devices.

Characteristic of the known technical solutions

From novel component technologies, there are growing demands on the output disks with regard to permanent gettering efficiency with good dimensional stability, in particular suppressed disk warping.

The majority of the known processes for producing getterable disks are based on the generation of crop-capable lattice defects in the volume (internal gettering) and on wafer surfaces, in particular on the wafer backsides (external gettering).

Gettereffizienz and capacity of such disorders in conjunction with their recoverability and thermally activated disc distortion are dependent on the nature of the disorders or the respective method used for their introduction. In particular, conventional methods which are based on the introduction of mechanically induced interference layers or primary disturbances in the backs of the disc have certain disadvantages compared to newer external gettes (methods such as laser irradiation (DE OS 2829983) and coating with poly-silicon (DE OS 2738195, HO1L 21 /

324). , -

One of the reasons cited for these disadvantages, the relatively easy thermal healability of the induced interference layers, obviously results from the severe controllability of movable dislocations, the generally dominating thermally induced secondary defect in such primary disturbances.

Among other things, therefore, the formation of stacking faults has been practiced as the predominant secondary defect with very slight disturbances of the disc rear side (DE OS 3148957), this type of defect, however, becomes unstable again at temperatures above 1200 ⁰ C.

A number of measures, such as overetching of the mechanically induced interfering layer (Takano, Y et al., Semiconductor Silicon, Minneapolis 1988, Proc. P743), are available for controlling moving dislocations, from which disc distortions to defect penetration also depend on surface active component areas of the disc. as well as ion implantation in this layer in conjunction with strained layers known.

It turns out, however, that these measures, even when used in combination, do not lead consistently to getterfähigen slices with reproducible shape behavior of the discs.

This is because in the generally desired, with respect to intensity and distribution or area density homogeneous primary disturbances due to typical thermally induced disc distortions during individual process steps of component manufacturing, locally differentiated mechanical stresses occur in the process disks or on their surfaces, which in turn local contribute in a different way to the activation and movement of dislocations.

Furthermore, the application of tensioning cover layers depending on the real shape of the output disks can lead to extremely different influencing of the disk shape.

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Object of the invention

The aim of the invention is to reduce its rejects in the production of microelectronic components and to increase their reliability.

Essence of the invention

The invention has as its object to provide a method for producing getterfähiger slices, which leads to permanent getterfähigen slices with uniform getter effect on the disc during the entire manufacturing process in suppression of a disc distortion.

The object is achieved using known process steps in the production of silicon wafers such as cutting, etching, chemical and / or mechanical polishing and additionally introduced lattice defects in the back of the wafer, thereon formed protective layers, for example silicon carbide (SiC), and thermal treatments in that lattice distortions in concentric or approximately concentric arrangement in terms of their. Surface form selected discs are introduced by means of a controlled tool and optionally applied a protective layer or a multi-layer protective layer system with respect to the resulting shape of the disc on the disturbed back.

Advantageously, the disruptive figures are introduced with circular or spiral geometry under local, radial and / or azirhulateral variation of intensity and / or surface density of the lattice defects.

It is furthermore expedient for the lattice defects to be omitted in the edge region and in the center of the disks and optionally in crystallographically distinguished directions or introduced with locally reduced intensity and / or surface density.

The selection of the slices in groups of comparable surface curvature takes place before or after polishing. In this case, a disk marking must be made in order to introduce the grid interference in the thus defined, preferably convex backs.

A preferred embodiment of the invention is that disturbances of comparable intensity and / or area density are introduced into disks with comparable surface curvature.

It is now expedient to provide the defective rear side of the pane with a protective layer or a protective layer system which, at room temperature, causes tensile stresses in surface areas close to the pane.

As a tool, one expediently uses truncated pyramids of diamond or other materials which are harder with respect to silicon and have radii of curvature between 5μ.ηη and 50μ.Γη.

Corresponding to the initial curvature of the disk, these tools are subjected to a normal force in the range of 10 nm to 2 N, the spacing of adjacent grid defects being in the range between 5 μm to 500 μm. It is also expedient here to preferably introduce the scribe-type lattice distortions in a depth range of 0.3 / .mu.m to 3.0 .mu.m, .mu.m, and preferably with a scribe spacing of 0.1... D, where D is the slice thickness is. All described problems of the back of the disc can also be introduced with laser beams.

Embodiment ""

The invention will be explained in more detail below with reference to exemplary embodiments. Example 1

In a n-SGT technology used B-doped (lOO) -oriented, 76mm slices are selected before polishing the later component surface in terms of their surface shape by two disc groups are sorted out whose deflection, for example, 3μ, ιτι ... 8μιη (Group 1), or 9μ, ηη ... 13μΓη (Group 2), be in a convex surface shape. This disc surface is defined as a later disc back. The introduction of scribe-like backside perturbations takes place by means of a diamond tool, the effective radius of curvature of which is selected such that a scratch depth of approximately 2 μm results for a normal force of approximately 50 μm (Group 1).

By disk rotation and tool translation spiral disturbances are formed, starting about 5mm from the disk center with a distance of adjacent interference (scratch distance) of about 50μ, ητι. Up to a distance of V3R (R = disk radius) from the disk center, the scribe distance is reduced continuously to about 30 / xm until V3R is kept constant and, from this distance from the disk center, again continuously increased to a maximum pitch distance ΙΟΟμ, ηη, with an edge region of about 4mm remains trouble-free.

Slices of group 2 are provided with a corresponding sturgeon figure, using the same tool with a normal force of about 35OmN.

Subsequently, in the formation of a protective layer of Si ₃ N ₄ , the thickness of which is chosen so that the later component side folds into a slightly convex shape, that is, discs of Group 1 receive a layer thickness of about 100nm, slices of group 2 has a layer thickness of about 150nm

 Example 2

From a quantity of 100mm B doped (HD disks for use in a bipolar technology, after polishing the component side, rear convex disks with a maximum deflection of ΙΟμ, πη are sorted out.) On the back are mechanically induced disturbances according to example Starting at about 7mm from the center with a scribe distance of about 100μηη, starting at a normal force of about 30OmN until V2R the normal force is continuously increased to about 60OmN and from V2R continuously reduced back to about 25OmN with an outer edge of about 5mm remains trouble-free.

Instead of abrasive tools - in addition to diamond, for example, SiC tools are suitable - corresponding disruptive figures are also generated by continuously operating lasers. A comparable variation of the interference intensity described above is obtained when a 25kHz modulated CW laser in the power range 1W ... 10W is driven.

Subsequently, the formation of a protective layer of SiC with a thickness of about 10nm, which causes a folding of the discs in a component-side slightly convex shape

 Example 3

76mm, P-doped, (100) oriented slices for use in CMOS technology are selected according to Example 2 and perturbed as in Example 1 by a programmable controller device, approximately 6mm from the center

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with a normal force of 20OmN maximum is started. Up to V3R, the normal force is increased to a maximum of 60 nm, which is kept constant until ² AjR. From V3R, a reduction is made to a minimum of 25OmN, leaving an edge of about 5mm free of interference.

In addition, the normal force is azimuthally varied by making a periodic reduction to ² h of the respective maximum force exerted when passing through (110> directions, ie every 90 °.) This compensates for the directional dependency of the offset paths in this extremely sensitive disc type.

The scribe distance is varied in the interval 30 / zm ... 300μ, ιη, according to Example 1, minimally close to V3R and at most near the edge and near the center of the slices.

The sealing of such treated discs is preferably carried out with SiC with a layer thickness of about 3 nm, which is produced by deposition or implantation of carbon and subsequent thermal stress in a reducing atmosphere at T> .1200X.

The heat treatment simultaneously leads to the formation of getter-capable dislocations, starting from the initially introduced lattice defects.

Claims (11)

-1- 685 69 Invention claims: 1. A method for producing getterfähiger silicon wafers using known process steps in the production of silicon wafers, such as cutting, etching, chemical and / or mechanical polishing, and using additionally introduced lattice defects in the back of the screen, optionally formed thereon protective layers, for example SiC, as well as thermal treatments, characterized in that - Grid interference introduced in a concentric or approximately concentric arrangement in terms of their surface shape selected slices by means of a controlled tool and optionally - A protective layer or a multi-layer protective layer system on the faulty back with respect to the resulting shape of the discs are applied. 2. The method according to item 1, characterized in that are introduced by using Störfiguren with circular or spiral geometry under local, radial and / or azimuthal variation of intensity and / or surface density grid interference. 3. The method according to item 1 and 2, characterized in that the grid interference in the edge region and in the center of the slices and optionally omitted in crystallographically excellent directions or introduced with locally reduced intensity and / or surface density. 4. The method according to item 1 to 3, characterized in that a selection of the discs takes place with respect to their surface curvature prior to polishing of the component-side disc surface. 5. The method according to item 1 to 4, characterized in that a selection of the discs takes place with respect to their surface curvature after polishing of the component-side disc surface. 6. The method according to item 1 to 5, characterized in that lattice disturbances are introduced into the convex-shaped disc backs of selected discs. 7. The method according to item 1 to 6, characterized in that disturbances comparable intensity and / or area density are introduced into slices with comparable surface curvature. 8. The method according to item 1 to 7, characterized in that the disturbed windscreen back is provided with a protective layer or a protective layer system, so that tensile stresses are caused at room temperature in the near-surface disk area. 9. The method according to item 1 to 8, characterized in that used as tools truncated pyramids of diamond or other harder with respect to silicon materials with radii of curvature between 5 / xm ... 50μ.ιτι and these tools with a normal force in the range 1OmN ... 2 N are charged, the distance between adjacent lattice defects in the range 5 ^ .m ... 500 / xm is. 10. The method according to item 8, characterized in that grid-like arranged grid interference in a depth range between 0.3μ, ΓΠ ... 3,0μ, ιτι and preferably with a scribe distance of 0.1 D ... 1.0D are introduced, where D is the slice thickness. 11. The method according to item 1 to 8, characterized in that are used as tools laser beams.