Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Total dielectric isolation
Reexamination Certificate
1999-06-18
2002-01-01
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Total dielectric isolation
C438S459000, C438S464000, C438S977000
Reexamination Certificate
active
06335258
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention relates to a production method for a thin film of solid material on a support, particularly when said solid material and said support have different thermal behavior. The thin film may be of a semiconductor material or not. The invention also relates to the structure obtained by said production method.
2. Background Art
Numerous methods for producing thin films of solid material are known. Said methods depend on the type of material and of the thickness of the preferred film. Thin films of a solid material can therefore be applied to the face of a part by being propelled, sprayed, electroplated etc. A thin film can also be obtained by thinning a plate of the preferred material using mechanical chemical or chemical abrasion, the thin film obtained then being stuck or bonded onto the part being used as a support.
Generally, a thin film is bonded to a face of a part to alter the properties of the part superficially.
In the field of semiconductors, thin films for semiconductors are also often made for example to manufacture substrates called “Silicon On Insulator”. Different methods for producing semiconductor thin films have been developed. One of the most recent methods is based on the fact that the ions of a rare gas or hydrogen implanted in semiconductor material cause weakened areas to form at a depth similar to the average penetration depth of the ions. French document 2 681 472 discloses a method that uses this property to obtain a thin film of semiconductor material. Said method consists in subjecting a plate of the preferred semiconductor material and that comprises a flat face to the following stages:
a first implantation stage in which the flat face of the plate is bombarded with ions to create a layer of “gaseous micro-bubbles” in the volume of the plate and to a depth similar to the penetration depth of the ions, said layer separating the plate by a lower area that constitutes the substrate mass and an upper area that constitutes the thin film. The ions are chosen from the ions of rare gas or of hydrogen gas;
a second stage in which the flat face of the plate is put into close contact with a support (or stiffener) that comprises at least one layer of rigid material. Said close contact can be achieved using an adhesive substance applied to the faces that have been previously prepared and heat and/or electrostatic treatment to allow inter-atomic bonding between the support and the plate;
a third stage consisting of heat treatment of the plate and support assembly at a temperature that is higher than the temperature during which the implantation was effected and that is high enough to create a separation between the thin film and the substrate mass. The temperature is approximately 400° C. for silicon.
The present document proposes the following explanation of the various phenomena reported. Firstly, the initial stage is carried out by beaming ions onto a flat face of a semiconductor material plate, the plane of said flat face being more or less parallel to a main crystallographic plane when the semiconductor material is perfectly monocrystalline or slightly inclined relative to a main crystallographic plane of the same indices for all the grains if the material is polycrystalline. A layer of “gaseous micro-bubbles” is therefore created in the volume of the plate. Said layer is located at a depth similar to the average penetration depth of the ions and demarcates two areas in the volume that is separated by said layer: an area intended to constitute the thin film and an area that constitutes the rest of the substrate. “Gaseous micro-bubbles” refers to any cavities or micro-cavities created by the implantation of hydrogen gas or rare gas ions in the material. The cavities may be extremely shallow, i.e. of very slight depth, for example of only a few inter-atoms, or they may be more or less hemispherical or any shape other than the two above-mentioned shapes. Said cavities may or may not include a gaseous phase. During the third stage the heat treatment is effected at a temperature high enough to cause the separation between the two regions. Said separation is achieved by the crystalline being rearranged in the semiconductor material, for example by the micro-cavities increasing in size and/or as a result of pressure from the micro-bubbles.
This method would appear to be suitable for any type of solid material, whether crystalline or not. It is possible for this method to be applied to dielectric, conducting and semi-insulating materials as well as amorphous semiconductor materials. Furthermore, this method does not basically alter the properties of the material to which it is applied.
The implantation of hydrogen or rare gas ions can therefore also cause micro-cavities to form in solid materials other than a crystalline semiconductor material. Subsequent heat treatment- can lead to splitting in the material mass if the implantation stage is carried out in such a way as to obtain a layer of micro-cavities.
Furthermore, the heat treatment stage that causes splitting is preferably defined in relation to a thermal budget that depends on the thermal budget of the ionic implantation stage and of the dose and the power of ions implanted and any other thermal budgets resulting from other stages. Therefore, under certain conditions annealing may occur at a lower temperature to that used during implantation.
However, the application of this method may present certain problems when the substrate in which a thin film is demarcated and the stiffener have different thermal dilation coefficients, or at least if they are too different. If this is the case, during the heat treatment stage competition occurs between the adherence forces retaining the implanted substrate and the stiffener that is in close contact, the forces being due to the differences in thermal dilation coefficients (that tend to separate the substrate from the stiffener) and the forces that cause splitting in the micro-cavities, said splitting being caused by the implantation of ions.
It is not usually easy to determine which force will be the stronger during the heat treatment stage. However, the inventors of the present invention have emphasized the fact that a separation may occur at the interface when the substrate is put into contact with the stiffener during said heat treatment and not in the area of the micro-cavities when the materials that constitute the substrate and the stiffener have different thermal dilation coefficients.
In order to implement the method for producing a thin film according to French document 2 681 472, the definition may be given as two materials having different thermal dilation coefficients within a given temperature range when said materials are brought into close contact with one another, thus creating thickness elements that are considered adjacent that are not able to withstand heat treatment within the given temperature range. This results in the two elements separating.
Disclosure of the Invention
To overcome this drawback, the present invention proposes to apply the heat treatment stage to the assembly consisting of the stiffener and the implanted substrate that come into close contact when at least one of said elements has taken the shape of a thin layer. When this occurs, the thin layer retains enough elasticity to withstand the distortion caused by the other material without forcing the two materials to separate.
The invention therefore plays on the thickness of one of the elements of the assembly in order that said element, which has become sufficiently thin, is capable of adapting to the distortions to which it is subject by the other element during the heat treatment stage. A split in the plane of the micro-cavities can therefore occur without causing problems for achieving the preferred thin film.
The aim of the invention is therefore a method for producing a thin film made of a first material on a support and a second material, said method comprising:
an ionic implantation stage during which a face of a substrate
Aspar Bernard
Barge Thierry
Bruel Michel
Burns Doane Swecker & mathis LLP
Commissariat a l'Energie Atomique
Niebling John F.
Pompey Ron
LandOfFree
Method for making a thin film on a support and resulting... 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 on a support and resulting..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making a thin film on a support and resulting... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2817836