POLYCRYSTALLINE MATERIAL HAVING LOW MECHANICAL STRAIN; METHOD FOR PRODUCING A POLYCRYSTALLINE MATERIAL

Abstract

A polycrystalline material having low mechanical strain is provided. The polycrystalline material includes one or multiple layers of a first type and one or multiple layers of a second type. The layers of the first type and the layers of the second type each include at least one polycrystalline material component. The layers of the first type have a smaller average crystal grain size than the layers of the second type, a layer of the first type and a layer of the second type being situated, at least in part, one above the other in an alternating sequence, and it being the case for the transition between the layers of the first type and the layers of the second type to be abrupt or continuous.

Claims

1-12. (canceled)

13. A polycrystalline material having low mechanical strain, comprising: one or multiple layers of a first type; and one or multiple layers of a second type; wherein the layers of the first type and the layers of the second type each include at least one polycrystalline material component, and wherein the layers of the first type have a smaller average crystal grain size than the layers of the second type, a layer of the first type and a layer of the second type being situated, at least in part, one above the other in an alternating sequence.

14. The polycrystalline material of claim 13, wherein adjacent layers of the first type and of the second type are in each case formed, at least in part, in direct contact with one another.

15. The polycrystalline material of claim 13, wherein the crystal grain size at the boundary between at least one layer of the first type and a layer of the second type adjacent to the one layer of the first type changes continuously or abruptly, in particular the crystal grain size at the boundary between all layers of the first type and the respective adjacent layers of the second type changing continuously or abruptly.

16. The polycrystalline material of claim 13, wherein within the layers of the first type, the crystal grain size decreases or increases, or initially decreases and then increases, in a preferred direction, in particular within the layers of the second type, the crystal grain size decreasing or increasing, or initially decreasing and then increasing, in a preferred direction.

17. The polycrystalline material of claim 13, wherein the layers of the first type and the layers of the second type are each formed as closed layers.

18. The polycrystalline material of claim 13, wherein the polycrystalline material component includes polycrystalline silicon.

19. The polycrystalline material of claim 13, wherein the polycrystalline material is situated on a substrate.

20. The polycrystalline material of claim 13, wherein the polycrystalline material includes a plurality of layers of the first type and a plurality of layers of the second type, in particular a layer of the first type and a layer of the second type being situated in each case one above the other in an alternating sequence.

21. A method for producing a polycrystalline material having low mechanical strain, the method comprising: depositing and/or growing layers of a first type and layers of a second type, via at least one depositing/growing arrangement; wherein the polycrystalline material includes one or multiple layers of the first type and one or multiple layers of the second type, wherein the layers of the first type and the layers of the second type each include at least one polycrystalline material component, the layers of the first type having a smaller average crystal grain size than the layers of the second type, and a layer of the first type and a layer of the second type being situated, at least in part, one above the other in an alternating sequence.

22. The method of claim 21, wherein the depositing/growing arrangement for depositing and/or for growing includes at least one chamber, the depositing and/or the growing of the layers of the first type and of the layers of the second type taking place in the chamber, at least one source gas being used for growing and/or depositing the layers of the first type and/or the layers of the second type, the depositing/growing arrangement for depositing and/or for growing including in particular an epitaxy unit.

23. The method of claim 21, wherein during the depositing and/or during the growing of the layers of the first type, a different temperature prevails in the chamber than during the depositing and/or during the growing of the layers of the second type.

24. The method of claim 21, wherein a different source gas is used for depositing and/or for growing the layers of the first type than for depositing and/or for growing the layers of the second type.

25. The polycrystalline material of claim 13, wherein the polycrystalline material is situated on a substrate, in particular a wafer or a chip.

26. The polycrystalline material of claim 13, wherein the polycrystalline material is situated on a substrate, in particular a wafer or a chip, on a separating layer of the substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 schematically shows a cross-sectional illustration of a polycrystalline material according to a first specific embodiment of the present invention.

[0019] FIG. 2 schematically shows a cross-sectional illustration of a polycrystalline material according to a second specific embodiment of the present invention.

[0020] FIG. 3 schematically shows a cross-sectional illustration of a polycrystalline material according to a third specific embodiment of the present invention.

[0021] FIG. 4 schematically shows a cross-sectional illustration of a polycrystalline material according to a fourth specific embodiment of the present invention.

[0022] FIG. 5 schematically shows a cross-sectional illustration of a polycrystalline material according to a fifth specific embodiment of the present invention.

DETAILED DESCRIPTION

[0023] FIG. 1 shows a polycrystalline material 5 having low mechanical strain according to a first specific embodiment of the present invention. Polycrystalline material 5 is situated on a separating layer 7. Separating layer 7 may include or be made of silicon oxides, for example. It is likewise possible for separating layer 7 to include other material components, for example nitrides, LNO, etc., or to be made of at least one of these components. It is likewise possible for separating layer 7 to be made up of a combination of such material components.

[0024] Polycrystalline material 5 includes a layer of a first type 1 and a layer of a second type 2, as well as a second layer of second type 2. The arrangement of the layers of polycrystalline material 5 is situated on separating layer 7, separating layer 7 being formed on a top side of substrate 6. A layer of first type 1 is situated above the layer of second type 2 (and in the illustrated specific embodiment is in direct contact with the layer of second type 2). A second layer of second type 2 is situated above the layer of first type 1 (and in the illustrated specific embodiment is in direct contact with the layer of first type 1). The layers of first type 1 have a smaller average crystal grain size (grain size) than the layers of second type 2.

[0025] According to further specific embodiments of the polycrystalline material according to the present invention, it is likewise possible for a layer (or a plurality of layers) of a third type (which, for example, contains a different material component than the layers of first type 1 and of second type 2, or contains the same material components as the layers of first type 1 and of second type 2, and has an average crystal grain size that is smaller than the average crystal grain size of the layers of second type 2, but larger than the average crystal grain size of first type 1) to be formed between a layer of first type 1 and a layer of second type 2.

[0026] According to further specific embodiments of the polycrystalline material according to the present invention, it is likewise possible for a (gas-filled) space to be formed, at least in part, between a layer of first type 1 and a layer of second type 2.

[0027] FIG. 2 shows a polycrystalline material 5 having low mechanical strain according to a second specific embodiment of the present invention. Polycrystalline material 5 includes three layers of a first type 1 and four layers of a second type 2. The arrangement of the layers of polycrystalline material 5 is situated on separating layer 7, separating layer 7 being formed on a top side of substrate 6. The layers of first type 1 and the layers of second type 2 are situated one above the other and in direct contact with one another in an alternating sequence. The layers of first type 1 have a smaller average crystal grain size (grain size) than the layers of second type 2.

[0028] FIG. 3 shows a polycrystalline material 5 having low mechanical strain according to a third specific embodiment of the present invention. Polycrystalline material 5 includes three layers of a first type 1 and four layers of a second type 2. The layers of first type 1 and the layers of second type 2 are situated one above the other and in direct contact with one another in an alternating sequence. The layers of first type 1 have a smaller average crystal grain size (grain size) than the layers of second type 2. Polycrystalline material 5 is thus situated on a separating layer 7 only in partial areas. In other areas, separating layer 7 has been removed below polycrystalline material 5. For some uses of polycrystalline material 5 (for microelectromechanical systems, for example), separating layer 7 is subsequently removed, so that polycrystalline material 5 (at least in parts) is not situated on a separating layer 7. This is advantageous, for example, when polycrystalline material 5, for example in the areas in which separating layer 7 has been removed below polycrystalline material 5, is used for freely movable structures (within microelectromechanical systems).

[0029] FIG. 4 shows a polycrystalline material 5 having low mechanical strain according to a fourth specific embodiment of the present invention. Polycrystalline material 5 includes four layers of a first type 1 and four layers of a second type 2. The layers of first type 1 and the layers of second type 2 are situated one above the other and in direct contact with one another in an alternating sequence. The arrangement of the layers of polycrystalline material 5 is situated on separating layer 7, separating layer 7 being formed on a top side of substrate 6. Within an individual layer of first type 1, the crystal grain size increases in a preferred direction. In FIG. 4, the preferred direction points vertically upwards, away from substrate 6. Within an individual layer of second type 2, the crystal grain size likewise increases in the same preferred direction. Despite the increasing crystal grain size in the preferred direction in each case within the layers of first type 1 and the layers of second type 2, the layers of first type 1 in each case always have a smaller average crystal grain size than the layers of second type 2. According to such a fourth specific embodiment, it is possible, for example, for the crystal grain size to continuously increase (i.e., for a continuous progression of the crystal grain size to be provided) from a layer of first type 1 to an adjacent layer of second type 2. In FIG. 4, for example the lowermost layer of first type 1 and the lowermost layer of second type 2 thus continuously merge into one another.

[0030] FIG. 5 shows a polycrystalline material 5 having low mechanical strain according to a fifth specific embodiment of the present invention. Polycrystalline material 5 includes three layers of a first type 1 and four layers of a second type. The layers of first type 1 and the layers of second type 2 are situated one above the other and in direct contact with one another in an alternating sequence. The arrangement of the layers of polycrystalline material 5 is situated on separating layer 7, separating layer 7 being formed on a top side of substrate 6. Within an individual layer of first type 1, the crystal grain size initially decreases in a preferred direction and then increases. In FIG. 5, the preferred direction points vertically upwards, away from substrate 6. Within an individual layer of second type 2, the crystal grain size initially increases in the same preferred direction and then decreases. Despite the increasing crystal grain size in the preferred direction in each case within the layers of first type 1 and the layers of second type 2, the layers of first type 1 in each case always have a smaller average crystal grain size than the layers of second type 2. According to this fifth specific embodiment, it is possible for the crystal grain size to continuously progress between (all) adjacent layers of first type 1 and of second type 2. In this way, for example a polycrystalline material may be produced which has a continuous progression of the crystal grain size in a preferred direction (for example, perpendicular to the surface area of the layers) over its entire extent.

[0031] The List of reference numerals is as follows: [0032] 1 first type [0033] 2 second type [0034] 5 polycrystalline material [0035] 6 substrate [0036] 7 separating layer