Semiconductor device manufacturing: process – Bonding of plural semiconductor substrates
Reexamination Certificate
2000-02-14
2001-10-16
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Bonding of plural semiconductor substrates
C438S458000, C438S515000, C438S526000, C438S766000, C438S798000, C148SDIG001, C156S250000
Reexamination Certificate
active
06303468
ABSTRACT:
TECHNOLOGICAL FIELD
The invention relates to a method of manufacturing a thin film of solid material. This method, in particular, allows the transfer of a thin film of homogeneous or heterogeneous solid onto a support made up of a solid material of the same kind or of a different kind.
STATE OF THE PRIOR TECHNOLOGY
Document FR-A-2 681 472 describes a method of manufacturing thin films of semiconductor material. This document discloses that the implantation of a rare gas or hydrogen into a substrate made of semiconductor material is able to cause the formation of micro-cavities or micro-bubbles (sometimes given the name “platelets”) at a depth close to the mean depth of penetration of the implanted ions. If this substrate is brought into intimate contact, through its implanted surface with a stiffener and a heat treatment is applied at sufficient temperature, it causes an interaction between the micro-cavities or micro-bubbles leading to a separation of the semiconductor substrate into two parts: a thin semiconductor film adhering to the stiffener on the one hand, and the remainder of the semiconductor substrate on the other hand. The separation takes place at the place where the micro-cavities or micro-bubbles are present. The heat treatment is such that interaction between the micro-bubbles or micro-cavities created by implantation induces a separation between the thin film and the rest of the substrate. Therefore there is transfer of a thin film from an initial substrate to a stiffener being used as a support for this thin film.
This method can also be applied to the manufacture of a thin film of solid material other than a semiconductor material (a conductive or dielectric material) whether crystalline or not.
If the thin film defined in the substrate is sufficiently rigid by itself (because of its thickness or because of its mechanical properties) a self-supporting film can be obtained after the transfer annealing. This is what document FR-A-2 738 671 discloses.
Contrary to this, in the absence of a stiffener, if the film is too thin to induce the fracture over the whole width of the substrate, bubbles appear at the surface conveying the presence of micro-fissures at the level of the mean depth of implantation of the ions. In this case, the heat treatment does not produce self-supporting layers but only produces flakes.
In the document FR-A-2 681 472, the heat treatment is defined by the annealing temperature in a step subsequent to the implantation step. This annealing temperature is greater than the implantation temperature and has to be such that it causes the separation between the thin film and the rest of the substrate.
The documents quoted above specify that the heat treatment is carried out at a temperature greater than the implantation temperature. Document FR-A-2 681 472 indicates that, in the case of a substrate made of silicon, the implantation temperature is preferably between 20° C. and 450° C. and that for the annealing, a higher temperature is necessary (for example a temperature of 500° C.
However, in certain cases and for certain applications, a high heat treatment temperature can present disadvantages. In effect, it can be advantageous to obtain cleavage of the substrate at temperatures considered to be low, in particular at temperatures lower than the temperature of implantation. This is important notably in the case where the transfer brings together materials with different thermal coefficients of expansion.
It can be advantageous to carry out the ionic implantation step at a high temperature, a temperature which can be higher than the temperature used for the heat treatment step. The interest in this resides in the fact that, if there is no restriction on the implantation temperature, a high implantation current density can be provided without being obliged to cool the substrate. The duration of the implantation can then be very much reduced.
In addition, between the ionic implantation step and the heat treatment (or annealing) step bringing about cleavage, the implanted surface can be treated, for example with the intention of creating electronic circuits in the case of a substrate made of semiconductor material. These intermediate treatments can be adversely affected if the annealing temperature is too high.
DESCRIPTION OF THE INVENTION
The invention allows the problems of the prior art to be resolved. The inventors of this invention have, in effect, discovered that it is possible to reduce the annealing temperature if one takes into account a thermal budget of the heat supplied to the substrate during the course of various steps of the method (ionic implantation step, possibly the adhesion of the substrate to the stiffener, possibly intermediate treatments and the annealing step that permits the separation). By thermal budget, it is understood that for a step where heat is supplied (for example, during the annealing step), one must not be concerned only with the temperature but with the combination of time and temperature when heat is supplied to the substrate.
By way of example, for a substrate made of silicon and weakly doped, implanted with a dose of 5.5×10
16
ions H
+
/cm
2
of energy 69 keV, at a temperature of 80° C. for around 5 minutes, cleavage appears with a thermal budget, in the case of an isothermal annealing, which depends as has been seen on the time-temperature combination. This thermal budget is 2 hours 15 minutes at 450° C. If the implanted dose is greater, for example, for a substrate made of weakly doped silicon implanted with a dose of 10
17
ions H
+
/cm
2
of energy 69 keV at a temperature of 80° C. for 5 minutes, the thermal budget necessary to obtain cleavage is less than previously. This budget is, for example, 2 minutes 22 seconds at 450° C. or 1 hour 29 minutes at 300° C. Hence cleavage occurs for thermal budgets, in the case of an isothermal annealing, which are different to the previous cases but which still depend on the time-temperature combination. The choice of thermal budgets can also depend on the type of material and its doping level when it is doped.
By way of example, for a strongly doped silicon (for example 10
20
boron/cm
3
) which is implanted with a dose of 5.5×10
16
ions H
+
/cm
2
of energy 69 keV at a temperature of 80° C. for 5 minutes, cleavage is obtained for a thermal budget of 4 minutes 15 seconds at 300° C. or 1 hour 43 minutes at 225° C.
In the case where the thermal treatment is carried out with a progressive rise in temperature, the thermal budget applied to substrates during this rise in temperature must be taken into account since it contributes to the cleavage.
In a general way, The choice of the thermal budget to be used in order to obtain fracture depends on the whole group of thermal budgets applied to the basic material or to the structure starting with the implantation step. All these thermal budgets constitute a thermal balance sheet which allows cleavage of the structure to be achieved. This thermal balance sheet is formed by at least two thermal budgets: that of the implantation and that of the annealing.
It may include, depending on the application, other types of budgets for example: a thermal budget to reinforce the molecular bonds at the adhesion interface or to create these bonds and one or more thermal budgets for the production of active elements.
Hence an objective of the invention is a method of manufacturing a thin film of solid material that includes at least the following steps:
a step of ionic implantation through one face of a substrate of said solid materials using ions capable of creating in the volume of the substrate and at a depth close to the mean depth of penetration of the ions, a layer of micro-cavities or micro-bubbles, this step being carried out at a particular temperature and for a particular length of time,
an annealing step intended to bring the layer of micro-cavities or micro-bubbles to a particular temperature and for a particular length of time with the intention of obtaining cleavage of the substrate on both sides of t
Aspar Bernard
Bruel Michel
Bowers Charles
Commissariat A l'Energie Atomique
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Sarkar Asok Kumar
LandOfFree
Method for making a thin film of solid material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making a thin film of solid material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making a thin film of solid material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2617724