DD228935A1 - FORMSTABLE SEMICONDUCTOR DISC AND METHOD FOR THE PRODUCTION THEREOF - Google Patents

Abstract

The invention relates to the preparation of silicon disks with stabilized form for the production of integrated components. The task is to unify the contraction forms of silicon wafers and to maintain them via the device manufacturing process. The object is achieved by generating disk-side interference and / or cover layers as a function of deflection classifications of the output disks or by selectively curved separation grinding of the single crystals. figure

Description

-3- 685

It has also been proposed to influence the shape of the disk by means of layers formed on the back side of faulty disks, which cause macroscopic tensile stresses in silicon disks. It turns out, however, that this method does not lead to success for all actually occurring disc shapes to success, in particular is limited, at the front highly convex output discs.

Object of the invention

The aim of the invention is to improve the mechanical stability of semiconductor wafers and thus to increase the yield in the manufacture of semiconductor devices.

Essence of the invention

The invention has as its object to provide a dimensionally stable semiconductor wafer and a method for their production, which leads to tight toleranced shape of the discs at the beginning and during the cycle of component manufacturing and is particularly suitable, a slightly convex curvature of the component-side surface (called in the further front) to secure the discs. The object is achieved according to the invention by starting from a convex disk curvature of the front side as the operating condition for the component production and the semiconductor disk being dimensionally stabilized on the back by means of covering and / or interference layers. Either circular disks with chamfers or circular disks with chamfers and the circular ring opening step are used.

For the production of cover layers, preference is given to silicon compounds having the elements oxygen, nitrogen and carbon, either by reaction of these elements with the backside disc material at high temperatures or by deposition from the gas phase.

Desired compressive or tensile stresses can be regulated over the thickness of these layers. Particularly advantageous are silicon carbide (SiC) layers, which generate tensile or compressive stresses depending on the choice of layer thickness and are chemically and thermally extremely resistant. It is expedient that the interference layer is introduced by means of a mechanically abrasive engagement as a nearly concentric lattice disorder.

To stabilize the convex disc curvature, it is now useful for silicon discs with concave front to provide them with a noise and / or cover layer on the back, which causes tensile stresses there and whose thickness is adapted to the curvature of the silicon wafer.

Accordingly, silicon discs are provided with a convex front with a noise and / or cover layer, which causes compressive stresses there and whose thickness is adapted to the curvature of the silicon wafer. With these measures, a wide range of output disc shapes with slightly convex biased faces can be adjusted and maintained over wide areas of the device manufacturing cycle. In both cases, the strength of the interference and / or cover layer, or their macroscopic stress component, and the respective disc thickness and size is adjusted. It is also advantageous to generate the interference layer by diffusion of impurities into the wafer rear side, wherein the pre-occupation with these foreign atoms is carried out in a conventional manner or with the aid of ion implantation. Suitable ions without Dotiercharakter are for example those of the elements carbon, germanium, argon. Conventional annealing processes are used to convert the atoms which are alien to silicon to lattice sites in the silicon monocrystal. The near-surface introduction of foreign atoms or their incorporation on silicon lattice sites optionally allows the generation of tensile or compressive stresses on the selection of suitable elements with the silicon deviating covalent atomic radius.

The method, the object of the invention is achieved by the known method of cutting the silicon monocrystals is guided so that substantially convex or concave to the crystal rod out curved disks, with a special water supply to the interface and / or a defined, unilateral dressing of the Diamondboardes are applied. It is expedient, after the production of silicon wafers, to divide them into groups with regard to their production-related, random curvature shape and to select them according to the extent of the curvature.

After this selection and classification, the stabilization measures according to the invention (application of a backside impurity and / or cover layer) follow, which can be repeated during the component fabrication process. The advantages of the inventive solution are above all that brought by the inventive measures a large variety of forms of silicon output disks in a necessary for modern VLSI device technologies defined, slightly convex front curvature and obtained stable in this form.

embodiment

The invention will be explained in more detail below with reference to embodiments. The accompanying drawing is based on silicon single crystals grown by the Czochralski process or the zone melting process, where selections and classifications according to the invention are carried out according to known process steps of wafer production.

In the case of cut-off grinding, a targeted direction of a single direction of curvature can be achieved by equipping the internal board grinding machine with a non-contact monitoring device, which detects the deflection of the diamond cutting machine from the ideal cutting direction during the cutting process. By modifying the flow of water to the interface and / or a defined, one-sided dressing of the diamond board, a deflection of the diamond cutting disc is produced in the desired direction and size.

The consequence of this is that the diamond disc is not straight but curved through the single crystal rod and thus defines defined curved discs. The back side of the later convex polishing surface must be marked accordingly.

It is also favorable to select according to the "etching" step of the disks, in which the interference layers on both sides of the disk are removed and the mechanical stresses are thus eliminated Classification, the discs are preferably measured with a non-contact deflection meter, thereby marking the concave side, as well as a classification by size groups made.

Also possible is a selection after the steps "Lapping" or "Polishing". Since the later front face of the disc is already fixed, a selection must be made in concave or convex faces before the classification into size classes of the curvature can be carried out with a non-contact measuring device.

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In general, the disk quality of the classification groups 2A should now be adjusted by further measures according to the invention.

Example 1:

At relatively low thermal stress by device technologies, the formation of interference layers for adjusting discs according to the invention is sufficient.

Preferably for technologies diel 000 ⁰ C does not exceed the thermal stress and be used for the continuous automatic Chargierprogramme.

Class 1 A slices are converted to the desired slice class 2A by a high-dose implantation of carbon (10 ^le cm ^-2 , 250 keV), followed by a conventional heat treatment at 550 ° C, 1 h.

In contrast, disks Class 2B with Ge low dose (10 ¹⁴ cm ^"2, 120 keV) and slices of Class 2C also with Ge (5 x 10 ¹⁵ cm ^-2, 180 keV) implanted and at 550 ⁰ C, 1 h healed.

Example 2:

Discs which are exposed to a higher thermal load are preferably provided, according to the described classification, with a cover layer of SiC or SiC compounds, if appropriate with an interfering layer formed thereunder.

Thus, for a CMOS technology, the disk shape is advantageously set by means of the formation of a cover layer, the resulting macroscopic disk stress being regulated by the method for covering layer formation and the respective predetermined layer thickness.

Thus, wheel backs of classes 1 A, 1 B and 1 C are first coated with carbon black, whereby a hydrocarbon mixture of acetone and benzene is burned. Subsequently, a brief heat treatment in a reducing atmosphere at 1 25O ⁰ C such that a thin SiC layer of about 10 .. 30 nm forms by reaction with the Si surface. This causes a stable transformation into the desired slice class 2A.

Slices of class 2 B are provided for this purpose by pyrolytic decomposition of tetramethyl-silane at 800 ⁰ C with a Si-C bonds-containing layer having a thickness of about 40 nm. For Class 2C wafers, the layer thickness is increased to about 70 nm.

In addition to the thickness-dependent tensile or compressive stress SiC has the advantage of high chemical resistance and a barrier effect for impurity diffusion.

For use in a bipolar technology, in which particularly high demands are placed on the dimensional stability of the discs, the formation of a disruptive layer is advantageously carried out, on which in turn a covering layer is deposited.

Mechanically induced, approximately concentric disturbances such as those produced by means of fine grinding (for example by means of a cup grinding wheel) proved to be favorable.

Since such perturbations are known to cause a slightly concave curvature of the opposing disk surface, Si ₃ N ₄ layers with a high tensile stress component should be used (about 150 nm).

Claims (12)

-2- 685 70 Invention claim: 1. dimensionally stable semiconductor wafer for producing microelectronic semiconductor devices, characterized in that the front of the disc is defined convexly curved and that the semiconductor wafer is stabilized on the back by means of cover layers and / or interference layers. 2. Dimensionally stable semiconductor wafer according to item 1, characterized in that the silicon discs are circular discs with chamfers. 3. Dimensionally stable semiconductor wafer according to item 1, characterized in that the silicon discs are annular discs with chamfers and with a circular opening opening section. 4. dimensionally stable semiconductor wafer according to item 1-3, characterized in that the back-side covering layer is a silicon compound with carbon and / or nitrogen and / or oxygen. 5. Dimensionally stable semiconductor wafer according to item 1-3, characterized in that the rear interference layer is introduced by means of a mechanical abrasive intervention, almost concentric lattice disorder. 6. dimensionally stable semiconductor wafer according to item 1, 4 and 5, characterized in that silicon discs are provided with concave front with interference and / or cover layers, so that there are tensile stresses on the back, over the thickness of the rear interference and / or cover layers of the curvature of the silicon wafers are adapted. 7. dimensionally stable semiconductor wafer according to item 1, 4 and 5, characterized in that silicon discs are provided with a convex front with a noise and / or cover layer on the back, so that compressive stresses exist on the back, the thickness of the sturgeon - And / or cover layers of the curvature of the silicon wafers are adapted. 8. dimensionally stable semiconductor wafer according to item 1-3, characterized in that an interference layer is introduced by diffusion of impurities at the back of the silicon wafer. 9. Dimensionally stable semiconductor wafer according to item 1-3, characterized in that a disruptive layer is introduced and cured by implantation of ions, for example carbon, germanium, argon ions. 10. A method for producing a dimensionally stable semiconductor wafer according to item 1, characterized in that the curvature of the semiconductor wafer is produced by targeted cutting-off. 11. A method for producing a dimensionally stable semiconductor wafer according to item 1, characterized ^ characterized in that the silicon wafers are classified according to the curvature shape (concave or convex) in groups and classified according to the extent of curvature and that the interference and / or outer layers be generated according to the groups and classes. 12. A method for producing a dimensionally stable semiconductor wafer according to item 1 and 7, characterized in that the production of the cover layers is repeated in the course of the cycle of component production. For this 1 page drawing Field of application of the invention The invention relates to a dimensionally stable semiconductor wafer and to a method for the production thereof for microelectronic components with a high degree of integration Characteristic of the known technical solutions LSI and VLSI device technologies are known to be particularly demanding ah exact adherence to dimensional stability of the silicon wafers at the beginning of the cycle of device fabrication as well as its subsequent course in each lithographic sub-step. High temperature treatments of the silicon wafers are generally carried out between these lithographic substeps. Despite sophisticated execution of the high-temperature treatments (optimal furnace profile, exact arrangement of silicon wafers, adapted temperature-time program, for example Ramp), it can lead to permanent changes in the shape of the silicon wafers, due to the high temperature treatments, distortions or Verbeuungen, which Inaccuracies, blurring in the following lithographic process and ultimately lead to failure of the device. The prior art for the production of silicon wafers is characterized by a polished silicon wafer production line, which usually begins at the nearly cylindrical single crystal grown dislocation-free from the crucible. The monocrystal is exactly crystallographically oriented and ground exactly cylindrical, also chamfered by grinding and finally cut into slices (with sufficient excess thickness of the slices) by means of an internal-board cut-off machine. The silicon wafers are freed in the near-surface areas of grinding and cutting defects of the crystal lattice by etching a sufficiently thick layer of the surface. Before the etching step, a lapping or fine grinding step may be provided to improve the shape of the silicon wafers. Nevertheless, finished polished silicon wafers may have quite different shapes in terms of deflection and evenness within a certain scattering range. It is possible to distinguish convex and concave portions of the surface of the polished silicon disks. These variations have a disadvantageous effect in the manufacture of components. For example, the thermal stress induced defect formation in the volume of the silicon wafers is dependent on their initial curvature in the polished state, as in Leroy, B .; Plangouven, C .; Journ. Electrochem. Soe. 127, 961 (1980). Furthermore, difficulties may arise in aspirating the discs when lithographic steps are to be performed on back convex or non-uniformly curved silicon discs. To improve the dimensional stability of semiconductor material wafers, it has already been proposed to make a recess connected to the outer edge in the semiconductor wafer, which is expediently carried out before the etching step (WP 210373). In order to stabilize the shape of the silicon wafers over the entire cycle of device fabrication, it has recently been proposed to provide the back of the silicon wafers with deep, almost continuous trenches and to build the semiconductor devices in alignment with these trenches (DE OS 3304255 / HO1L21 / 80). It is obvious that such a silicon wafer requires a high-precision one-off production with corresponding costs. Also, it must not be overlooked that the use of silicon wafers with complex shapes in any case requires certain changes in technological equipment.