KR20060033809A - Method of detaching a semiconductor layer - Google Patents

Abstract

The invention relates to a method of detachment of a layer from a wafer of material chosen from semiconductor materials, the method comprising the steps consisting of: creating an embrittlement zone in the thickness of the wafer, the said embrittlement zone defining the layer to be detached in the thickness of the wafer; subjecting the wafer to a treatment to perform detachment of the layer, at the level of the embrittlement zone; characterized in that during the creation of the embrittlement zone, a localized starting region of this zone is constituted, at the level of which the embrittlement zone locally has greater embrittlement, so that this starting region corresponds to a super-embrittled region of the embrittlement zone.

Description

Semiconductor layer separation method {METHOD OF DETACHING A SEMICONDUCTOR LAYER}

The present invention relates to a method of separating a layer from a wafer of selected material in a semiconductor material, consisting of the following steps:

Creating an embrittlement zone in the wafer thickness layer that defines a layer separated from the wafer thickness layer,

At the soft zone level, processing the wafer so that layer separation is performed.

Methods of this type are known. These methods make it possible to obtain thin layers of micron or below thickness as possible.

The layer may be a semiconductor material such as silicon.

The SMARTCUT® method is an example of how to utilize these steps.

The resulting layers should also conform to very stringent surface condition specifications.

Therefore, it is common to find a roughness specification that should not exceed 5 ohms strong as the rms (root mean square) value.

Roughness measurements are generally performed by applying an atomic force microscope (AFM).

With this type of device, the AFM point scans the surface and measures roughness up to 1 × 1 μm ² and up to 1 × 1 μm ² , more rarely up to 50 × 50 μm ² or 100 × 100 μm ² .

It is also possible to measure the surface roughness by other methods, in particular by 'haze' measurement. This method has the advantage that it is possible to quickly specify the roughness uniformity over the entire surface.

These hazes are measured in ppm and are due to the method of utilizing the light reflectivity properties of the specified surface and correspond to the 'background noise' of light emitted from the surface due to their micro-roughness.

As mentioned above, the surface state specification of the separation layer is very strict in the semiconductor field.

According to these specifications, it is also desired that the roughness possible over the surface of the separation layer be homogeneous.

The present invention seeks to provide as even roughness distribution as possible over the separation layer surface.

This particular aspect has not been dealt with in the present method, for example WO 02/05344 and EP 938 129 do not mention this uniform roughness aspect in the separation wafer layer.

In addition, this strict specification may be associated with the rest of the wafer after separation (this remaining portion is referred to as 'negative').

In order to achieve this specification it is possible to provide complementary surface treatment steps after separation.

Such complementary treatments are, for example, using polishing, sacrificial oxidation, and / or supplemental annealing steps.

However, in order to simplify and accelerate the layer fabrication process, it is desirable to lower the dependency on these complementary treatments.

It is an object of the present invention to address this need.

In order to achieve this object, the present invention provides:

Creating an embrittlement zone in the wafer thickness layer that defines a layer separated from the wafer thickness layer,

A method for separating layers in a wafer of a material selected from a semiconductor material, comprising processing the wafer such that layer separation is performed at the soft zone level.

During the soft zone generation step, a local initial zone having a locally weaker zone, which is a super-embrittled zone of the soft zone, is created in the soft zone,

-Heat treatment for applying a substantially uniform amount of heat to the wafer over the entire weak area.

Preferably, but not by way of limitation, the features of the method are as follows:

The weak zone is created by atomic species implants, and during implants the initial zone is created by local overdose implants.

Separation is thermal annealing,

Annealing is carried out so that the amount of heat corresponding to the energy required for the separation to be applied to the wafer,

Different heating elements arranged to face the wafer are selectively controlled during annealing,

Separation is initiated at the initial dose level during annealing,

Separation propagates from the initial zone to the entire weak zone.

Other aspects, objects and advantages of the invention will become more apparent upon reading the detailed description of the preferred embodiment of the invention in conjunction with the accompanying drawings:

1 is a schematic assembly drawing of an annealing apparatus usable in the present invention,

2 is a more detailed schematic view of a portion of this device,

3 is a schematic diagram of the annealing device usable in the present invention corresponding to a second embodiment of this device.

Fragile  produce

The first step of the method according to the invention is to create a weak region that defines a layer to separate within the semiconductor material wafer thickness layer.

The wafer may be silicon, for example.

According to a preferred embodiment of the present invention, which corresponds to an alternative SMARTCUT® type method, the weak zone generation is performed by atomic species implants.

According to the art, such implants are performed such that uniform concentrations of implanted atomic species appear in the fragile region.

For this purpose, the implant dose is the same over the entire soft area.

In the case of the present invention, in contrast, the implant is performed by a local overirradiation implant in a predetermined area of the wafer.

This area of the wafer will therefore accept more radiation of atomic species than the rest.

Such locally implanted overirradiation can be obtained by first implanting the wafer in a spatially uniform manner and then overirradiating the implant locally in the desired area.

Alternatively, one can anticipate scanning the wafer surface by displacing the species beam of the implanter onto the wafer surface.

In this case, kinematics of beam displacement across the wafer surface are defined such that spatially uniform implants are performed on the wafer surface, except in certain areas where an overexposure implant is desired, such an excess of implants Probe generation is fixed for a sufficient time.

In this configuration, it is the implant beam that the wafer is fixed and displaced.

In a controlled manner it is also possible to displace the wafer facing the fixed beam.

In all cases, the resulting weak areas will include areas where the concentration of the implanted species is locally higher.

This appears locally at the level of this area of the soft area, with greater softness between the layer being separated and the wafer portion corresponding to the rest, and thus this area (which can be seen later) Is the super-embrittled area of the weak area.

Such weak areas are preferably located on the wafer peripheral.

Since it is possible to precisely control the implant properties, the creation of such regions with higher concentrations of implant species is simply performed.

Thus, the step of constructing the fragile region is performed to generate a local region having a locally greater fragility in this region, which corresponds to the overfragile region in the fragile region.

This region of the fragile region will be referred to formally as a 'starting region'; The meaning of these terms will be apparent from the description below.

This area of the soft zone is localized; For example, it may be an area that covers each angular sector of a several degree on the outer surface of the weak area.

Alternatively, this particular region may include all wafer outer surfaces.

In this case, each sector covered by the initial region may be up to 360 °. The width of this region with a crown shape is narrow and is substantially less than one centimeter.

Separation treatment

Once the soft region has been created on the wafer with the initial region, a process is performed to separate the layer from the rest of the wafer at the soft region level for the wafer.

desirable Example

According to a preferred embodiment of the present invention having a weak area implanted by local overexposure, annealing is applied, not a separation process.

Through this annealing, coalescence of micro-bubble formed at the weak area level by the implant is possible.

Such annealing is preferably carried out under the condition of applying as much heat as possible to the wafer.

In the case of the present invention, during annealing, separation begins in the initial zone and propagates throughout the soft zone so that complete separation is achieved.

Applicants note that when performing a 'conventional' separation annealing where the heating elements are centered on heating configurations where all heating elements supply the same thermal energy, the separation is 'hot points' or 'hot areas'. Note that it starts at the 'hot regions' level.

This hot zone corresponds to a location that receives more heat locally in the soft zone due to temperature non-uniformity in the furnace. They are typically located in the upper region of the wafer (in the vertical direction).

For conventional SMARTCUT® methods, it may be wise to use these hot regions for initiation of separation (eg, using non-uniform calorie distribution in different regions of the wafer).

However, in the case of the present invention, the initiation of the separation is carried out in the initial zone, in particular it is possible to limit the range of rough areas associated with the separation and to suppress these hot zones (which above all have a uniform roughness distribution Get it).

Several solutions are possible for this purpose.

1 shows a first embodiment of the annealing apparatus applicable in the present invention.

The annealing applied to each wafer is aimed at facilitating the separation of the material layers defined in the wafer thickness layer by the weak areas.

1 device 10 comprises a heating enclosure 100 for receiving one or more wafers T to be annealed.

The longitudinal axis of the device 10 is vertical, which device is thus of vertical oven type.

It can be noted that the wafers are arranged vertically in this closed space, not horizontal as is known.

The wafers are housed in a cage 110, which is itself supported by the support 111.

The support 111 is seated on a cover 112 that blocks the device throat 120.

Wafer holding means 130 is provided for introducing the wafers into the apparatus 10 and removing them after annealing.

The closed space portion 100 has an opening 101 disposed opposite the neck 120. Heat-carrying gas may be introduced into the closed space through the opening.

Multiple heating configurations 140 surround the closed space 100.

These heating arrangements may be electrodes that are heat dissipable, for example, by electrical supply.

FIG. 2 shows in more detail the closed space 100, wafers T, and heating configurations 140 (these numbers are reduced in this figure for clarity).

Means not shown in the figure can selectively control the supply for each heating configuration, and thus selectively control the heating power of each of these configurations.

In this way, the vertical distribution of the amount of heat applied to the wafer during heating is controlled.

Applicants have noted that, as shown in Figures 1 and 2, with the idea of placing the wafer vertically, the vertical temperature gradient can be represented by using a conventional vertical oven.

Due to the selective supply control for the heating configurations 140, a spatially uniform amount of heat can be applied over the entire soft area of the wafer.

This can be visualized, for example, by measuring the haze produced on the surfaces of the layers after separation.

Typically, lower heating configurations will be supplied more than upper heating configurations, thus compensating that the heat rises naturally inside the closed space and thus the upper portion of the closed space exhibits a higher temperature.

Thus, it can be assured that the overall amount of heat applied to the wafer is uniform over the entire weak area of each wafer.

1 and 2 correspond to a preferred embodiment of the annealing apparatus that can be applied in the present invention.

However, it is also possible to achieve uniform application of the total calorific value at other settings.

3 shows an apparatus 20 capable of performing annealing to a wafer T or a plurality of wafers according to the present invention.

The wafer (s) extend substantially horizontally in the heating closed space 200.

The closed space portion is provided with an opening 201 for introducing a heat-carrying gas.

Apparatus 20 has heating configurations shown collectively as reference numeral 240.

These heating arrangements can be placed only on the wafers, but the same similar heating arrangements can also be placed on the bottom side of the wafer.

The heating configurations can be a series of respective heating configurations extending in the same horizontal plane (eg electrode or heating plate).

Each heating configuration may be a circular ring disposed concentrically with other configurations having different diameters.

While the wafers are annealed, the configurations can also be placed concentrically.

Here, means (not shown) are provided for selectively and individually controlling each heating arrangement.

Thus, it is ensured that the overall amount of heat applied to the wafers is uniform along the wafer weak area.

Heating configurations 240 may also be a single electrode of the 'heating plate' type that may control temperature distribution.

Configurations 240 can also be replaced with controlled infrared lamps, and the supply for each can be controlled individually.

Electrode-type configurations 240 (such as concentric annular rings, for example) can be combined with an infrared lamp that provides supplemental heating that can locally control the amount of heat applied to the fragile region, resulting in an overall uniform heat output. Configure.

In any case, in all embodiments of the present invention, the heating apparatus can perform uniform heating on the wafer and apply a uniform amount of heat to the weak regions of the wafers.

It should be recalled that this characteristic aspect is ignored in already published methods such as WO 02/05344 and EP 938 129.

In operation, the annealing device according to the invention thus applies a uniform amount of heat to the weak areas of the wafers.

During this annealing, the amount of heat received by each wafer corresponds to the amount of energy required to separate the layers from the wafer.

Whatever setting is used to perform this annealing, a local separation of layers from the wafer is obtained at the initial region level for each wafer.

This initial separation propagates spontaneously over the entire area of weakness due to sufficient heat supplied to the wafer.

Applicants note that this method results in a particularly low surface roughness for the separation layer.

This roughness is more uniform, which is a particular advantage obtained by the present invention.

In contrast, in the case where conventional separation annealing is applied to a wafer of a weak region without an initial region, separation is initiated at the mentioned hot region level during annealing.

In this case, the local roughness of the separated layer is observed to be more severe at the hot area level than the general layer surface roughness.

In a preferred embodiment of the invention, such non-uniform roughness can be avoided.

The present invention thus provides, in a preferred embodiment, an alternative to the conventional SMARTCUT® version:

In the case of the conventional SMARTCUT® method, the implant is performed substantially uniformly across the wafer surface, during separation annealing, separation is initiated according to the nonuniformity of the heat applied to the wafer,

In the case of an alternative SMARTCUT® according to a preferred embodiment of the present invention, on the contrary, a non-uniform implant is carried out with a local overexposure, and during separation annealing, a uniform amount of heat applied to the wafer is applied.

Etc Example

As noted above, it is possible to practice the invention in accordance with preferred and other embodiments that fall in the alternative case of the SMARTCUT® method.

According to these embodiments, an initial region defined such that the region of weakness between the layer being separated and the rest of the wafer is locally fragile is created at the wafer region of weakness.

During processing for the purpose of separating the layers from the wafer, in all cases separation begins in the initial zone and propagates over the entire soft zone surface.

Claims (7)

Creating an embrittlement zone in the wafer thickness layer that defines a layer separated from the wafer thickness layer, A method for separating layers in a wafer of a material selected from a semiconductor material, comprising processing the wafer such that layer separation is performed at the soft zone level. During the soft zone generation step, a local initial zone having a locally weaker zone, which is a super-embrittled zone of the soft zone, is created in the soft zone, A heat treatment for applying a substantially uniform amount of heat to the wafer over the entire weak area. The method of claim 1, wherein the fragile region is created by an atomic species implant, wherein the initial region during the implant is created by a local overdose implant of the atomic species. The method according to claim 1, wherein the separation treatment is thermal annealing. The method of claim 1, wherein the annealing is performed to apply a heat amount corresponding to the energy required for separation to be performed to the wafer. The method of claim 1, wherein different heating elements arranged to face the wafer are selectively controlled during annealing. The method of claim 1, wherein the separation is initiated at the initial dose level during annealing. The method of claim 1, wherein the separation propagates from the initial zone to the entire soft zone.

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