Wafer bonded virtual substrate and method for forming the same

Abstract

A method of forming a virtual substrate comprised of an optoelectronic device substrate and handle substrate comprises the steps of initiating bonding of the device substrate to the handle substrate, improving or increasing the mechanical strength of the device and handle substrates, and thinning the device substrate to leave a single-crystal film on the virtual substrate such as by exfoliation of a device film from the device substrate. The handle substrate is typically Si or other inexpensive common substrate material, while the optoelectronic device substrate is formed of more expensive and specialized electro-optic material. Using the methodology of the invention a wide variety of thin film electro-optic materials of high quality can be bonded to inexpensive substrates which, serve as the mechanical support for an optoelectronic device layer fabricated in the thin film electro-optic material.

1 . A virtual substrate comprising a non-silicon device film bonded to a handle substrate, wherein: (1) the device film and the handle substrate comprise different materials with different coefficients of thermal expansion; and (2) strain states of the device film and the handle substrate are such that there is a first temperature that is greater than room temperature and less than 900 degrees Kelvin, where the strains of the device film and handle substrate are equal.  
   
   
       2 . The virtual substrate of  claim 1 , wherein a magnitude of a bow of the virtual substrate over a range of temperatures between 300 and 900 K is lower than a magnitude of a bow in the same virtual substrate with a first temperature at or near room temperature.  
   
   
       3 . The virtual substrate of  claim 1 , where the first temperature ranges from 400 to 900 K.  
   
   
       4 . The virtual substrate of  claim 1 , wherein the first temperature equals to the temperature at which the handle substrate is bonded to the device film.  
   
   
       5 . The virtual substrate of  claim 4 , wherein the first temperature ranges from 400 K to 700 K.  
   
   
       6 . The virtual substrate of  claim 1 , wherein (1) a coefficient of thermal expansion (CTE) difference between the handle substrate and device film is greater than zero; (2) the device film is in compressive strain at room temperature; and (3) the magnitude of the strain in the virtual substrate at temperatures above room temperature is below the magnitude of the strain for an identical virtual substrate bonded at room temperature.  
   
   
       7 . The virtual substrate of  claim 1 , wherein (1) the CTE difference between the handle substrate and device film is less than zero; (2) the device film is in tensile strain at room temperature; and (3) the magnitude of the strain in the virtual substrate at elevated temperatures above room temperature is below the magnitude of the strain for an identical virtual substrate bonded at room temperature.  
   
   
       8 . The virtual substrate of  claim 1 , wherein (1) the device film is germanium; (2) the handle substrate is silicon; and (3) the first temperature is between 300 and 900 degrees Kelvin.  
   
   
       9 . The virtual substrate of  claim 1 , wherein (1) the device film is indium phosphide; (2) the handle substrate is silicon; and (3) the first temperature is between 300 and 900 degrees Kelvin.  
   
   
       10 . The virtual substrate of  claim 1 , wherein (1) the device film is gallium arsenide; (2) the handle substrate is silicon; and (3) the first temperature is between 300 and 900 degrees Kelvin.  
   
   
       11 . The virtual substrate of  claim 1 , wherein the strain states of the device film and handle substrate have been engineered to control a bow of the virtual substrate at a temperature above room temperature.  
   
   
       12 . The virtual substrate of  claim 1 , wherein the strain states of the device film and handle substrate have been engineered to control at least one of a carrier mobility and a bandgap of the device film at operating temperatures above room temperature.  
   
   
       13 . The virtual substrate of  claim 1 , wherein the device film comprises a semiconductor material suitable for fabrication of optoelectronic devices.  
   
   
       14 . The virtual substrate of  claim 13 , wherein the device film comprises germanium or a compound semiconductor material and the handle substrate comprises a silicon, GaAs, glass, quartz or sapphire substrate.  
   
   
       15 . The virtual substrate of  claim 14 , wherein the device film is selected from Ge, GaN, GaAs and InP films and the handle substrate comprises a silicon substrate.  
   
   
       16 . The virtual substrate of  claim 1 , wherein the device film comprises a ferro-electric oxide.  
   
   
       17 . The virtual substrate of  claim 1 , further comprising a strain compensation layer located on an opposite side of the handle substrate from the device film.  
   
   
       18 . The virtual substrate of  claim 1 , wherein the device film and the handle substrate comprise semiconductor materials and an interface between the device film and the handle substrate has a resistance of 3.5 ohms cm 2  or less.  
   
   
       19 . A method for engineering a strain state of a virtual substrate, comprising: (1) ion implantation of a device substrate; (2) initiating bonding of the device substrate and a handle substrate at a controlled temperature in order to control a resultant strain state in the final virtual substrate; and (3) removing a portion of the device substrate to leave a device film bonded to the handle substrate, thereby forming the virtual substrate.  
   
   
       20 . The method of  claim 19 , wherein the bonding is initiated at a temperature above room temperature.  
   
   
       21 . The method of  claim 20 , wherein the bonding is initiated at a temperature between 400 and 900 K.  
   
   
       22 . The method of  claim 20 , wherein the handle substrate and the device substrate are maintained at different temperatures when the bonding is initiated.  
   
   
       23 . The method of  claim 19 , wherein (1) the device film is germanium, gallium arsenide or indium phosphide; and (2) the handle substrate is silicon or gallium arsenide.  
   
   
       24 . The method of  claim 19 , wherein the strain states of the device film and handle substrate have been engineered to control the bow of the virtual substrate at a temperature above room temperature.  
   
   
       25 . The method of  claim 19 , wherein the strain states of the device film and handle substrate have been engineered to control at least one of a carrier mobility and a bandgap of the device film at operating temperatures above room temperature.  
   
   
       26 . The method of  claim 19 , wherein the device film comprises a semiconductor material suitable for fabrication of optoelectronic devices.  
   
   
       27 . The method of  claim 19 , further comprising forming a strain compensation layer on an opposite side of the handle substrate from the device film.  
   
   
       28 . The method of  claim 19 , wherein the device film and the handle substrate comprise semiconductor materials and an interface between the device film and the handle substrate has a resistance of 3.5 ohms cm 2  or less.  
   
   
       29 . A method for engineering a strain state of a virtual substrate, comprising: (1) ion implantation of a device substrate; (2) initiating bonding of a handle substrate and the device substrate where the temperature of the handle substrate is different than the temperature of the device substrate at a time of bond initiation; and (3) removing a portion of the device substrate to leave a device film bonded to the handle substrate, thereby forming the virtual substrate.  
   
   
       30 . The method of  claim 29 , wherein the bonding is initiated at a temperature above room temperature.  
   
   
       31 . The method of  claim 30 , wherein the bonding is initiated at a temperature between 400 and 900 K.  
   
   
       32 . The method of  claim 29 , wherein the temperature of the device substrate is greater than the temperature of the handle substrate at the time of bond initiation.  
   
   
       33 . The method of  claim 29 , wherein (1) the device film is germanium, gallium arsenide or indium phosphide; and (2) the handle substrate is silicon or gallium arsenide.  
   
   
       34 . The method of  claim 29 , wherein the strain states of the device film and handle substrate have been engineered to control the bow of the virtual substrate at a temperature above room temperature.  
   
   
       35 . The method of  claim 29 , wherein the strain states of the device film and handle substrate have been engineered to control at least one of a carrier mobility and a bandgap of the device film at operating temperatures above room temperature.  
   
   
       36 . The method of  claim 29 , wherein the device film comprises a semiconductor material suitable for fabrication of optoelectronic devices.  
   
   
       37 . The method of  claim 29 , further comprising forming a strain compensation layer on an opposite side of the handle substrate from the device film.  
   
   
       38 . The method of  claim 29 , wherein the device film and the handle substrate comprise semiconductor materials and an interface between the device film and the handle substrate has a resistance of 3.5 ohms cm 2  or less.