Process for manufacturing transferable thin layer

Abstract

The invention relates to a process for the preparation of a semiconductor material comprising at least one entirely monocrystalline semiconductor layer, said process comprising the steps of preparation of the surface of a first substrate to receive a monocrystalline silicon layer; deposition by Plasma-Enhanced Chemical Vapor Deposition (PECVD) of a layer of monocrystalline silicon by epitaxial growth with a growth rate gradient on the silicon layer monocrystalline obtained in step (i); and epitaxial growth of a monocrystalline layer of a semiconductor material on the monocrystalline silicon layer obtained in step (ii), to thus obtain a material comprising at least one entirely monocrystalline semiconductor layer. The invention also relates to a multilayer material comprising a monocrystalline layer of semiconductor material.

Claims

1. A process for the preparation of a semiconductor material comprising at least one entirely monocrystalline semiconductor layer, said process comprising: (i) preparing a surface of a first substrate to receive a layer of monocrystalline silicon; (ii) depositing by Plasma-Enhanced Chemical Vapor Deposition (PECVD) a layer of monocrystalline silicon by epitaxial growth with a growth rate gradient on the first substrate prepared in (i); and (iii) epitaxial growing a monocrystalline layer of a semiconductor material on the monocrystalline silicon layer obtained in (ii), thereby obtaining a material comprising at least one entirely monocrystalline semiconductor layer.

2. The process of claim 1, wherein the process comprises, after the epitaxial growing in (iii), (iv) detaching at least the monocrystalline layer of semiconductor material formed by epitaxial growth at (iii) for its physical separation from the first substrate, and (v) transferring at least the layer of semiconductor material formed by epitaxial growth, onto a second substrate.

3. The process of claim 2, wherein the deposition technique (v) on the second substrate is chosen from a technique comprising: anodic bonding, or the use of silicone, a polyimide tape or a high temperature glue, or any combination thereof.

4. The process of claim 2, wherein the detachment (iv) of the monocrystalline layer of semiconductor material is carried out by mechanical or thermal treatment, or any one of their combinations.

5. The process of claim 1, wherein preparation (i) of the surface of the first substrate comprises the removal of oxides present on the surface of the first substrate intended to receive the silicon layer.

6. The process of claim 1, wherein said PECVD is implemented for the formation of a plasma forming SiH.sub.3 radicals then of a plasma forming silicon clusters.

7. The process of claim 1, wherein the temperature of PECVD (ii) and epitaxial growth (iii) is less than 400° C.

8. The process of claim 1, wherein the epitaxial growth (iii) is implemented with one or more elements chosen from among: Si, Ge, SiGe.

9. The process of claim 1, wherein the epitaxial growth (iii) is implemented with a technique chosen from among PECVD, CVD, MBE, or any of their combinations.

10. An entirely monocrystalline multilayer semiconductor material that may be obtained by a process according to claim 1, said entirely monocrystalline multilayer semiconductor material comprising a first substrate on which is deposited a monocrystalline silicon layer, said entirely monocrystalline material having a substrate/silicon layer interface having a peak hydrogen atom concentration greater than 1×10.sup.21 atoms/cm.sup.3.

11. The entirely crystalline multilayer semiconductor material according to claim 10, wherein the layer of monocrystalline silicon has a layer of an entirely monocrystalline semiconductor material on the face opposite to the first substrate.

12. An entirely monocrystalline multilayer semiconductor material that may be obtained by a process according to claim 1, said entirely monocrystalline multilayer semiconductor material comprising a first substrate on which is deposited a monocrystalline silicon layer, said entirely monocrystalline multilayer semiconductor material having a substrate/silicon layer interface having, by spectroscopic ellipsometry, oscillations greater than 0.2 ε, in the photon energy range from 1.5 to 3 eV.

13. The entirely crystalline multilayer semiconductor material according to claim 12, wherein the layer of monocrystalline silicon has a layer of a monocrystalline semiconductor material on the face opposite to the first substrate.

14. The entirely monocrystalline multilayer semiconductor material according to claim 11, wherein said entirely monocrystalline multilayer semiconductor material having a substrate/silicon layer interface has, by spectroscopic ellipsometry, oscillations greater than 0.5 ε, in the photon energy range from 1.5 to 3 eV.

15. The entirely crystalline monocrystalline multilayer semiconductor material according to claim 11, wherein said entirely monocrystalline multilayer semiconductor material having a substrate/silicon layer interface has, by spectroscopic ellipsometry, oscillations greater than 0.5 ε, in the photon energy range from 1.5 to 2.5 eV.

16. A semiconductor material characterized in that may be obtained by a process according to claim 1, said semiconductor material comprising at least one entirely monocrystalline semiconductor layer.

17. A multilayer semiconductor material that may be obtained by a process according to claim 1, said multilayer semiconductor material comprising a first substrate on which is deposited a monocrystalline layer of semiconductor material with a thickness of 1 nanometer (nm) to 10 micrometers (μm), and one or more layers of one or more other materials.

18. The multilayer semiconductor material according to claim 17, wherein the substrate is chosen from among: glass, a metal or metal alloy, a polymer, including one chosen from among co-polymers, a flexible material, an elastomer, or a thermoplastic elastomer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the figures:

(2) FIG. 1 represents a measurement by spectroscopic ellipsometry under the conditions of example 1.

(3) FIG. 2 represents a measurement by SIMS under the conditions of example 1.

DETAILED DESCRIPTION

Examples

Example 1

(4) Two multilayer materials were prepared, one according to a process according to the present invention with an epitaxial growth rate gradient of the monocrystalline silicon layer, the other, comparative, with a constant epitaxial growth rate by PECVD.

(5) A thin layer of 600 nm thick silicon was thus prepared according to these two PECVD processes.

(6) For the two samples (comparative and according to the invention), the silicon layer deposited by PECVD is deposited by direct growth on the cleaned silicon wafer (free of native oxide).

(7) For the example according to the present invention, three PECVD plasma conditions were used.

(8) The first PECVD deposition conditions are as follows:

(9) Temperature: 200° C.;

(10) Pressure: 240 Pa;

(11) Power: 35 mW/cm.sup.2;

(12) SiH.sub.4 flow rate: 2 sccm;

(13) H.sub.2 flow rate: 200 sccm;

(14) Duration: 60 sec.

(15) The second PECVD deposition conditions are as follows:

(16) Temperature: 200° C.;

(17) Pressure: 227 Pa;

(18) Power: 17 mW/cm.sup.2;

(19) SiH.sub.4 flow rate: 1 sccm;

(20) H.sub.2 flow rate: 200 sccm;

(21) Duration: 60 sec.

(22) The third PECVD deposition conditions are as follows:

(23) Temperature: 200° C.;

(24) Pressure: 307 Pa;

(25) Power: 35 mW/cm.sup.2;

(26) SiH.sub.4 flow rate: 4 sccm;

(27) H.sub.2 flow rate: 200 sccm;

(28) Duration: 1800 sec.

(29) For the comparative sample, the silicon layer was deposited by PECVD without an epitaxial growth rate gradient only according to the third PECVD deposition conditions.

(30) The results of spectroscopic ellipsometric measurements are illustrated in FIG. 1. It is noted that at low energy, the imaginary part of the pseudo-dielectric function εi exhibits oscillations which are characteristic of the porosity of the interface between the substrate (monocrystalline silicon wafer) and the silicon layer deposited by PECVD. The high porosity of the interface is detected for the sample according to the present invention as illustrated by a high amplitude of the low energy oscillations. The oscillation amplitude is significant compared to the comparative sample. It should be noted that in the higher energy part (greater than 3 eV), the spectrum is very similar to the silicon wafer, thus demonstrating the crystalline quality of the material according to the present invention.

(31) In FIG. 2, the hydrogen concentration profile characterized by SIMS should be noted for the two samples. For the sample according to the present invention, the interface is very porous with a strong accumulation of hydrogen on the surface in contact with the silicon wafer (up to 2.5×10.sup.21 atoms/cm.sup.3). Such a concentration peak was not observed in the comparative sample, the hydrogen concentration of which is approximately 3×10.sup.20 atoms/cm.sup.3.

(32) Then, for the material according to the invention, the transfer of the silicon layer was successfully carried out on glass, for example by anodic bonding at 200° C. for 10 minutes and then annealing at 200° C. for 5 minutes. On the contrary, for the comparative sample, under the same conditions, it is not possible to detach the layer deposited by PECVD. No detachment is observed even with annealing at 550° C. for 5 minutes, or even when the silicon wafer breaks.

(33) Thus, the process according to the present invention allows a simple transfer at low cost of a semiconductor material on a substrate that may be less expensive than silicon.

Example 2

(34) Under the same conditions as in Example 1, the thin layer of silicon was transferred to a flexible substrate.

(35) It is thus possible to obtain a crystalline semiconductor material on a flexible substrate.