KR20090122176A - Method of fabricating a hybrid substrate - Google Patents

Abstract

The invention relates to a method of fabricating a hybrid substrate comprising at least two layers of crystalline material that are bonded directly to each other. This method is noteworthy in that it comprises steps consisting in: implanting at least one category of atomic and/or ionic species into a donor substrate so as to form therein a weakened zone forming the boundary between an active layer and a remainder; subjecting the front faces of the donor substrate and of a receiver substrate, to a heat treatment between 900°C and 1200°C, under hydrogen and/or argon for a time of at least 30 seconds; bonding said front faces to each other; detaching said remainder; the nature, implantation dose and implantation energy of said species being chosen so that the defects induced by these species within the donor substrate allow the remainder of the donor substrate to be subsequently detached but do not develop sufficiently during said heat treatment to prevent the subsequent bonding or to deform the front face of the donor substrate.

Description

Method of fabricating a hybrid substrate

The present invention is directed to a method of making a hybrid substrate comprising at least two layers of crystalline material bonded to each other by direct bonding.

Substrates of this type can be used in the fields of optics, electronics or optoelectronics, and these terms are also commonly referred to as microelectronics, nanoelectronics, photomicro Optomicroelectronics, optonanoelectronics and component technology.

The two layers of the aforementioned materials may be layers of materials of the same or different nature, the term 'nature' means the chemical properties of the materials and their physicochemical properties and / or their It encompasses all of its crystalline orientations.

The term “direct bonding” of two layers or two substrates means molecular bonding (molecular boinding) without an intermediate layer such as an adhesive layer.

Such hybrid substrates are known to those skilled in the art as DSB (direct silicon bonding). Such substrates comprise an active silicon layer bonded directly to a receiving substrate made of silicon in different crystalline orientations, without the formation of an intermediary layer, in particular a buried oxide layer. It is thus possible to produce a substrate comprising a silicon layer having a (110) crystalline orientation bonded directly to a silicon support having a (100) crystalline orientation. Or vice versa.

If the receiving substrate is made of silicon carbide (SiC), it is possible to manufacture a hybrid substrate known to those skilled in the art as SopSiC (polycrystalline SiC phase silicon).

Such hybrid substrates are useful for the production of high performance microelectronic circuits.

C.Y., a supplement to the summaries published on pages 160-161 of the International Conference on Solid Equipment and Materials in Yokohama, 2006. Sung's paper, "Direct Silicon Bonded (DSB) Mixed Orientation Substrate for High Performance Bulk CMOS Technology," said An example of fabrication that transfers a 110 donor substrate to a (100) silicon receiving substrate is cited. The paper stated that such substrates do not require an insulating layer between the two layers bonded together.

In addition, the paper stated that hydrophobic type prebond preparation is preferred over hydrophilic type prebond preparation in the absence of SiO ₂ insulating layer in the final structure.

This means that a hydrophilic junction is formed during the preparation of the surface of the layer to be bonded, and that the oxide, which is buried in the final structure, must subsequently be removed, for example by a final annealing step at very high temperatures. Because. This completes the manufacturing method in this case.

However, such hydrogen end bonds adsorb particles that negatively affect the junction, so hydrophobic bonds associated with hydrogen end bonds are more difficult to implement.

There is also a method of obtaining a thin film of semiconductor material from a donor substrate, as known from US Pat. No. 6,020,252. This method injects a predetermined amount of rare-gas or hydrogen ions into a donor substrate at a predetermined temperature to create a weakened zone therein and allows the substrate to separate into two parts on each of the soft sides. It consists of a method of heat treatment at high temperature.

As described in the above document, the subsequent heat treatment alone is selected to form a microcavity sufficient to obtain a soft band in the substrate but insufficient microcavity to achieve separation. Separation requires the application of additional physical forces.

However, this document is not particularly relevant for surface preparation that allows good direct bonding.

It is an object of the present invention to overcome such drawbacks of the prior art. In particular, there is no need for bonding using an intermediate intermediate layer, and the bonding between the donor substrate and the receiving substrate is to provide a method for producing a hybrid substrate obtained by the transfer of layers, which is carried out through high quality hydrophobic bonding.

Summary of the Invention

To this end, the present invention is a hybrid substrate comprising at least two layers of crystalline material bonded directly to each other, one layer of which is 'active' derived from a crystalline substrate called a 'donor' substrate. Provided is a method of making a hybrid substrate comprising a layer of material called a layer.

According to the invention, the method comprises the following successive steps.

A weakened zone that injects at least one kind of atom and / or ionic species into the donor substrate and forms a boundary there between an active layer and the remainder of the donor substrate Forming);

One of the faces called the "front" face of the donor substrate and one of the "front" faces of a so-called crystalline substrate called a receiving substrate at 800 ° C. for at least 30 seconds in a gaseous atmosphere comprising hydrogen and / or argon. Heat treatment at a temperature of 1200 ° C. to give a so-called “prebonding preparaation” and to make the front face hydrophobic;

Joining the front faces directly together;

Performing the heat treatment of the two substrates under conditions to obtain a strong bond between them; And

Separating the remainder along the weakened zone by purely mechanical action.

The defect caused by these species in the donor substrate causes the remainder of the donor substrate to be subsequently separated, but not developed enough to prevent subsequent bonding or to deform the front side of the donor substrate during the pre-bonding preparation heat treatment. The properties, implant amounts, and implant energies of the atomic and / or ionic species are selected.

Other aspects of the present invention and the following may be carried out individually or in combination without departing from the scope of the present invention.

The pre-bonding preparation process is carried out under a gaseous atmosphere containing only argon;

The prebonding preparation is carried out under a gaseous atmosphere comprising only hydrogen;

The pre-bonding preparation process is carried out in a rapid thermal annealing (RTP) furnace;

The heat treatment to strengthen the bonding of the two substrates is carried out at a high temperature of 1100 ° C. or higher for a long time of at least two hours;

The species injected to form the fragile zone are selected from hydrogen, helium, fluorine, neon, argon, krypton and xenon;

The active layer of the donor substrate is a material selected from silicon (Si), (110) silicon, (100) silicon, silicon-germanium (SiGe), germanium (Ge), silicon carbide (SiC) and gallium nitride (GaN) It includes; And,

The receiving substrate at least partially comprises a material selected from silicon (Si), (110) silicon, (100) silicon and silicon carbide (SiC).

The features and advantages of the present invention will be apparent from the accompanying drawings and the description of the specification. However, this is intended to provide one specific embodiment of the present invention but not to limit the invention.

Description of the Preferred Embodiments

The various successive steps for the method can be briefly described as follows.

As shown in FIG. 1, the "donor" substrate 1 comprises two opposing sides 10 and 11, which are referred to as "front face" and "rear face", respectively. do.

As shown in FIG. 2, atoms and / or ionic species can be implanted into the donor substrate 1 to form a weakened zone 12 therein, which is called the active layer 13 and the substrate A boundary is formed between the remaining portions 14 of.

Conveniently, this implantation can be carried out via a sacrificial insulation layer 3, for example a layer of silicon dioxide (SiO ₂ ) deposited on the front side 10 of the substrate 1. .

Next, as shown in FIG. 3, the insulating layer 3 is removed.

Next, a preliminary bonding preparation process is performed to the said donor board | substrate 1 and the accommodating board | substrate 2, It demonstrates later in detail (refer FIG. 4).

The receiving substrate 2 comprises two opposing faces 20 and 21 called front and back, respectively.

Next, the front face 20 of the receiving substrate 2 is attached to the front face 10 of the donor substrate 1 by direct bonding (see FIG. 5).

The junction interface is the reference (4).

After the treatment for strengthening the bonding, as shown in Fig. 6, the remaining portion 14 of the donor substrate 1 is separated so that the active layer 13 is transferred to the receiving substrate 2 and the reference number 5 ), A hybrid substrate is obtained.

The various steps are now described in greater detail.

The donor substrate 1 and the receiving substrate 2 may or may not be composed of a semiconductor material.

In general, the material constituting the donor substrate 1 can be selected from crystalline materials that can create a dense distribution of cavities before the thermal annealing step by implanting atoms and / or ionic species.

For example, the material constituting the donor substrate 1 may be silicon (Si), (110) silicon, (100) silicon, silicon-germanium (SiGe), germanium (Ge), silicon carbide (SiC, silicon carbide). ) And gallium nitride (GaN).

The receiving substrate 2 is composed of a crystalline or amorphous material, for example, silicon (Si), (110) silicon, (100) silicon or silicon carbide (SiC), preferably monocrystalline silicon or polycrystalline Silicon carbide as well as polycrystalline silicon. It may be a semiconductor or an insulating material.

Two particular applications of the invention are that the donor substrate 1 and the receiving substrate 2 are both made of silicon, preferably monocrystalline silicon, and have different crystal orientations (e.g. (100), (110) or (111)). DSB-type substrate, or donor substrate 1, is made of silicon (preferably single crystal silicon) and the receiving substrate 2 is formed of SopSiC type substrate which is polycrystalline silicon carbide.

The donor substrate and the receiving substrate may also be multilayer substrates. In this case, however, the layer of material constituting the fronts 10 and 20 of the substrates 1 and 2 needs to meet the aforementioned specifications.

The step of implanting the atom and / or ionic species is such that, during the pre-bonding pretreatment heat treatment shown in FIG. It is carried out by selecting the type of injection, the amount of injection and the energy of injection so as not to be sufficient to prevent the subsequent bonding shown in FIG. 5 or to deform the front surface 10 to be bonded (see FIG. 6).

Examples of the atom and / or ionic species that can be implanted are hydrogen (H), helium (He), fluorine (F), neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe). .

These kinds are particularly suitable for implantation into the silicon substrate 1.

The selection of the species, their amounts and their implantation energies is made to avoid surface bubbling phenomena that typically occur when annealing, injecting the material in a standard manner.

It is also generally possible to co-implantation operations, ie continuously bombard the surface of the substrate with other species. For example, helium is first implanted followed by H ⁺ ions.

Likewise, the properties of the species, their amounts and their implantation energy are selected in such a way that the bubbling of the species to be injected is limited.

Thus, a simple injection or co-injection is one with an injection energy and amount of 20 to 500 keV, 1 × ^{10 14} at / cm ² to 1 × 10 ¹⁷ at / cm ² . In one example, helium atoms are implanted into the substrate at an energy ranging from about 30 to 200 keV in an amount ranging from 5x10 ¹⁶ to 1x10 ¹⁷ at / cm ² . In the case of argon atoms, the applied energy is about 200 to 500 keV and the dosage is about 1 x 10 ¹⁶ to 5 x 10 ¹⁶ at / cm ² .

In the case of co-injection, for example, hydrogen can be co-injected with fluorine and helium and hydrogen can be co-injected.

In the case of hydrogen / fluorine co-injection, the hydrogen is injected with an energy of 20-50 keV, in an amount of ¹ × 10 ¹⁵ -5 × 10 ¹⁶ H ⁺ / cm ² , while the fluorine is with an energy of about 150-200 keV, 1 × ^{10 14} To 1 × 10 ¹⁶ F ⁺ / cm ² .

For hydrogen / helium co-injection, the helium is injected at 1 × 10 ¹⁶ to ⁶ × ^{10 16} He ⁺ / cm ² with energy of 70 to 90 keV, while the hydrogen is at energy of about 70 to 90 keV, 1 × ^{10 15} to 6 × ¹⁰ Injected at ¹⁵ H ⁺ / cm ² .

In the injection, the reader can refer to the literature on the Smart Cut ^™ process.

Preferably the injection is carried out through the front side 10 as shown in FIG. 2.

Also preferably, all the implantation is carried out through a sacrificial oxide layer 3. This oxide 3 is formed thermally (for example in SiO ₂ for a silicon substrate), or a deposition technique known to those skilled in the art, such as chemical vapor deposition (CVD) or low pressure chemical vapor deposition (LPCVD) at atmospheric pressure. It is formed by vapor deposition by. These techniques are not described in detail below.

The oxide (3) is also a natural oxide.

The sacrificial oxide (3) is removed by immersing the substrate (1) in dilute dilute hydrofluoric acid (HF) solution or by placing it under an atmosphere of hydrofluoric acid vapor after implantation.

The removal of the sacrificial oxide film is preferably by a cleaning operation of RCA type in order to protect the front face 10 from contamination by particles. Treatment with a so-called RCA-clean chemical bath involves the following successive steps of the front side 10.

A bath of a solution known as SC1 (Standard Wash 1) consisting of a mixture of ammonium hydroxide (NH ₄ OH), hydrogen peroxide (H ₂ O ₂ ) and deionized water.

A bath known as SC2 (Standard Wash 2) comprising a mixture of hydrochloric acid (HCl), hydrogen peroxide (H ₂ O ₂ ) and deionized water.

As can be seen in FIG. 4, the pre-bonding preparation process is carried out at least about one side of (10) or (20) to be bonded at about 800 ° C to 1200 ° C under hydrogen and / or argon gas atmosphere without oxygen. Heat treatment.

Thus, the gaseous atmosphere is selected to include only one of hydrogen or only argon or a mixture of the two gases, or one or both of these in combination with other gases except oxygen. The duration of the treatment is at least 30 seconds and preferably does not exceed a few minutes.

The effect of the hydrogen and / or argon is to remove through the treatment the natural oxides that may be present on the surface, to form a protective film on this surface using hydrogen gas and to make the surface roughness very low.

This prebonding preparation also has the effect of making the treated surface hydrophobic. The effect was demonstrated by measuring the contact angle of water droplets to a value of 80 °. This value was higher compared to the typical 70 ° obtained after treatment of the "HF-last" type (Y. Backlund, Karin Hermasson and L. Smith, "Bond-strength measurements related to silicon surface hydrophilicity), "J. Electrochem. Soc., Vol. 1398, No. 8, 1992,).

The advantage of this treatment is that no species is absorbed on the treated surface. Since the hydrogen atoms are so small that they desorbs, they do not remain between their boundaries to form covalent bonds between the opposing fronts 10 and 20, but do not create defects due to the desorption of gas. Removed into the material.

This treatment is also of a dry type and differs from, for example, the HF-last treatment mentioned above. Therefore, it is simpler to perform this since there is no need for drying.

Finally, this pre-bonding pretreatment has the effect that the implanted ions, for example He ⁺ ions, are trapped and stabilized in the formed and expanded microcavities. It is embrittlement of the microcavity coalescing and the material injected into the zone. However, the injection conditions are chosen in such a way that the layer 13 is not separated from the residue 14 due to the coalescence phenomenon.

The pre-bonding preparation process can be performed in a chamber for which the atmosphere is controlled, for example a single wafer RTP (rapid thermal process) high temperature annealing. It is also possible to use existing furnaces if the substrates are processed in batches.

After the treatment mentioned above, the front faces 10 and 20 must be bonded to each other very quickly to minimize the risk of contamination by the surrounding atmosphere. This bonding step is shown in FIG. 5. It is also convenient to store the treated substrate in a chamber with a controlled atmosphere containing only inert gas, usually argon or nitrogen. Such treatment can be held time, i.e., donor substrate 1 and receiving. The time for which the substrates 2 are bonded to each other can be increased.

In addition, the surface subjected to the pre-bonding preparation is much less reactive than the surface treatment by the HF-last treatment mentioned above. This reduces the contamination of these surfaces with particles. Therefore, it can be industrialized simply.

As shown in Fig. 5, in the direct bonding step, each of the front surfaces 10 and 20 of the donor substrate 1 and the receiving substrate 2 are bonded to each other in close contact, that is, by molecular adhesion.

After the bonding step, a treatment for strengthening the bonding, that is, a treatment performed in the form of a long heat treatment is performed, and the heat treatment is performed at a high temperature of 1100 ° C. or more for at least two hours.

As can be seen in FIG. 6, the donor substrate 1 is separated from the remainder 14. As above, separation is purely by mechanical force. Separation by purely mechanical force is, for example, using a tool such as a knife to separate from one side of the substrate along the soft stand 12 by mechanical action, or to apply water or air jet at this point. . This type allows the structure to be rotated to facilitate the separation while purely mechanical separation is performed.

1 to 6 show the successive steps of the manufacturing method according to the invention.

Two examples of the present invention are provided as follows.

Example 1

Helium ions (He ⁺ ) were implanted into the (110) Si silicon substrate covered with a silicon oxide (SiO ₂ ) layer with a implantation energy of 50 keV, slightly less than 1 x 10 ¹⁷ He ⁺ / cm ² .

Next, the formed silicon oxide (SiO ₂ ) was treated with hydrofluoric acid (HF) solution and removed by washing with RCA-clean type.

The silicon donor substrate and the receiving substrate not only made of silicon but also having a crystalline orientation were subjected to pre-bonding preparation at 1050 ° C. for about 4 minutes under a gas atmosphere containing hydrogen and argon.

The substrates 1 and 2 were bonded to each other so that their front surfaces faced each other, and heat-treated at 1100 ° C. for 2 hours to bond them strongly.

Finally, the donor substrate was separated from the rest by inserting a knife with purely physical force.

The silicon / silicon DSB type substrate was obtained.

Therefore, this product has a high quality joint surface for future production of parts.

Example 2

Hydrogen / fluorine co-injection was performed on a (100) Si silicon substrate covered with a silicon oxide (SiO ₂ ) layer. The fluorine was injected at about 1 × ^{10 15} F ⁺ / cm ² . The injection energy is 180 keV. In the case of hydrogen, 4 x 10 ¹⁶ H ⁺ / cm ² was injected and the injection energy was 30 keV.

The formed silicon oxide was then treated with hydrofluoric acid (HF) solution and removed by washing with RCA-clean type.

The silicon donor substrate and the receiving substrate are made of polycrystalline silicon carbide (pSiC) and then pre-electrolyte ready at 800 ° C. for about 5 minutes in a gas atmosphere containing hydrogen.

The two substrates 1 and 2 were each bonded together through their front side and heat treated at 1000 ° C. for 3 hours to strengthen the bonding.

Finally, the donor substrate was completely physically separated from the rest by liquid jet injection.

Thus, the silicon-on-polycrystalline silicon carbide (SopSiC) substrate type can achieve significant high quality junction interfaces.

Claims (8)

A method of making a hybrid substrate comprising two layers of crystalline material to be bonded together, comprising a layer of material called an active layer derived from a crystalline substrate called a donor substrate,  Implanting at least one category of atomic and / or ionic species into the donor substrate to form a fragile zone 12 defining a boundary between the active layer and the remainder of the donor substrate; 800 ° C. for at least 30 seconds under a gaseous atmosphere containing hydrogen and / or argon to hydrophobize the front surface of one of the surfaces called the front surface of the donor substrate and the front surface of the crystalline substrate called the receiving substrate. Performing a so-called pre-bonding heat treatment at a temperature of from 1200 to 1200 ° C .; Joining the front faces directly together; Heat treating the two substrates under conditions that strongly adhere therebetween; And Separating the remainder along the fragile zone with purely physical force; Consists of successive steps, The defects caused by the species are such that the remainder of the donor substrate is subsequently separated but not developed sufficiently to prevent subsequent bonding during pre-bonding heat treatment or to modify the front side of the donor substrate. Or selecting the characteristics, implantation amount and implantation energy of the ionic species. The method of claim 1, wherein the pre-bonding preparation process is performed in a gaseous atmosphere containing only argon. The method of manufacturing a hybrid substrate according to claim 1, wherein the pre-bonding preparation process is performed in a gaseous atmosphere containing only hydrogen. The method of manufacturing a hybrid substrate according to any one of claims 1 to 3, wherein the pre-bonding preparation is performed in a rapid thermal annealing (RTP) furnace. The method according to any one of claims 1 to 4, Wherein the heat treatment for strengthening the bonding of the two substrates is performed by a long time heat treatment performed at 1100 ° C. or more for 2 hours or more. 6. The hybrid substrate of claim 1, wherein the species implanted to form the weakened zone is selected from hydrogen, helium, fluorine, neon, argon, krypton and xenon. 7. Manufacturing method. The method according to any one of claims 1 to 6, And the active layer of the donor substrate comprises a material selected from silicon, (110) silicon, (100) silicon, silicon-germanium, germanium, silicon carbide silicon, and potassium nitride. The method according to any one of claims 1 to 7, And the receiving substrate is at least partially composed of a material selected from silicon, (110) silicon, (100) silicon and silicon carbide.

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