JP6791880B2 - Parallel plate electric field application device using microwaves - Google Patents

Description

Related Application This patent application, which is not a provisional application, is a prior application of a US patent provisional application entitled "Device for Applying Parallel Plate Electric Field Using Microwaves" filed on January 29, 2015 on a completely common subject. Claim the priority interests of application 62 / 109,355, the entire contents of which are incorporated herein by this reference.

Background Advances in miniaturization of semiconductor devices have resulted in improved performance and increased storage capacity for many electronic devices. Manufacturing of semiconductor devices involves many process steps. One step is doping the semiconductor substrate that forms the source / drain junction. The ion implantation method is used to improve the electrical properties of a semiconductor substrate by implanting certain dopant impurities onto the surface of a semiconductor wafer. Commonly used dopants are boron, arsenic, and phosphorus. When using the ion implantation method, a post-annealing process is required to complete the activation process and repair any associated damage to the implanted area. Various annealing techniques can be used, depending on the amount of injection (the amount of atoms injected into the surface) and the injection energy (the depth of atoms into the surface). For example, the annealing technique can include various other versions including in-furnace treatment, rapid heat treatment (RTP), millisecond annealing (MSA), and laser annealing. However, there are disadvantages associated with each of these techniques, as described in US Pat. No. 7,928,021, the entire contents of which are incorporated herein by reference.

Within the solid-state device industry, experiments have been performed using microwave heating for this annealing process, but the use of microwave heating has suffered many disadvantages. In microwave heating, a multimode reaction chamber is used to heat / process a target substrate that is relatively larger than the wavelength of the microwave used. Inside a multimode chamber, microwave energies are coupled by modal excitation to control a local microwave field, also known as an electric field. The electric field may also be affected by the dielectric properties of the target substrate heated in the multimode chamber. If the target substrate is made of a material with a suitable dielectric, microwaves will flow to the target substrate at a higher concentration. Based on the electromagnetic properties of the microwaves inside the multimode chamber and the skin effect of the target substrate, the target substrate can penetrate it or form a current flow on its surface based on its conductivity.

Unfortunately, electric field concentrations can be difficult to monitor and control. For example, if the electric field concentration is strong enough, it will cause unwanted thermal runaway and arc unrelated to the microwave dielectric reaction, causing non-uniform heating and potential damage to the target substrate inside the multimode reaction chamber. May cause. A stirrer and rotating plate were used to attempt to make the electric field more uniform, and a metal foil layer was also used to change the field energy locally to the target substrate to be heated. However, each of these methods has faced the challenge of controlling, minimizing, or eliminating the formation of eddy currents in order to avoid the non-uniform heating caused by conventional eddy currents.

Another method of heating the target substrate is the most commonly used parallel plate reactor at radio frequency (RF), mainly due to technical limitations at higher frequencies. Therefore, independent parallel plate reactors are generally limited to frequencies in the RF band, creating a limited reaction within the target substrate due to the wavelength used. Prior art RF heating was only introduced to the solid state market as a bulk heater with no real difference in heating compared to other conventional heating methods such as infrared.

Abstract of the Invention The embodiments of the present invention solve the above problems and bring about a clear advance in the technique of annealing a semiconductor material. Specifically, embodiments of the present invention can provide annealing systems and methods for annealing target substrates such as semiconductors using industrial microwave heating and parallel plate reactions.

In some embodiments of the invention, the annealing system comprises a uniform microwave field generator, two plates held in close proximity to each other and / or parallel to each other, and two inside a uniform microwave field. The plate and turntable device coupled to the target substrate can be included. The uniform microwave field generator can generate a uniform microwave field, and the two plates can be held inside the uniform microwave field generator at a distance apart from each other. Specifically, the plates can be spaced close enough to each other to form a capacitive effect between the plates inside a uniform microwave field. The turntable rotates the plate and target substrate inside a uniform microwave field, creating a periodic change in the polarity of the microwave applied from the uniform microwave field to the target substrate, thereby producing eddy currents. It can flow at right angles to the plate and the target substrate.

Another embodiment of the present invention includes a method of annealing a semiconductor material, in which a target substrate made of the semiconductor material is placed between two plates inside a uniform microwave field, and a uniform microwave field. Includes creating a periodic change in the polarity of the microwave applied to the target substrate from. The periodic change results in a flow of eddy currents perpendicular to the target substrate and plate.

In yet another embodiment of the invention, the method of annealing a semiconductor material involves doping a parallel plate and then placing a target substrate made of the semiconductor material between the parallel plates inside a uniform microwave field. Including the step of placing. Doping may be sufficient to cause the parallel plates to react to a uniform microwave field, and the parallel plates may form a capacitive effect between the parallel plates inside the uniform microwave field. Can be placed close enough apart. The target substrate can include semiconductor materials doped with impurities. The uniform microwave field can include frequencies in the range 900 MHz to 26 GHz. The method then rotates the parallel plate and the target substrate inside a uniform microwave field, thereby creating a periodic change in the polarity of the microwave applied from the uniform microwave field to the target substrate. Can include steps. The periodic change can result in a flow of eddy currents perpendicular to the target substrate and parallel plates, thus resulting in uniform heating of the target substrate and selective heating of defects in the target substrate.

This abstract is provided to introduce in a simplified form the selected concepts further described in the detailed description below. This gist is not intended to identify the main or essential features of the claimed subject matter, but may also be intended to be used to limit the scope of the claimed subject matter. Absent. Other embodiments and advantages of the present invention will become apparent from the detailed description and accompanying drawings of the following embodiments.

Brief Description of Drawings Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of an annealing system configured according to various embodiments of the present invention. FIG. 2 is a schematic perspective view of an example target substrate heated by the annealing system of FIG. FIG. 3 is a schematic perspective view of another example target substrate heated by the annealing system of FIG. FIG. 4 is a flowchart of a method of annealing according to various embodiments of the present invention. FIG. 5 is a graph of bandgap vs. bulk mobility of the target substrate for various semiconductor materials. FIG. 6 is a schematic view of a target substrate that receives conventional microwave heating of the prior art, in which eddy currents are concentrated at both ends of the target substrate and flow substantially parallel to the surface of the target substrate. FIG. 7 is a schematic view of a target substrate between two plates undergoing mobile annealing using the method of FIG. 4, where eddy currents flow at right angles to the target substrate. FIG. 8 is a schematic view of a target substrate having a silicon crystal lattice having a defect inside. FIG. 9 is a schematic view of the target substrate of FIG. 8 that receives the conventional microwave heating of the prior art, and the eddy current at that time flows on the surface of the target substrate in parallel with the target substrate. FIG. 10 is a schematic view of the target substrate of FIG. 8 undergoing mobile annealing using the method of FIG. 4, and the eddy current at that time flows into the target substrate at a right angle to the target substrate.

These drawings are not intended to limit the invention to the particular embodiments disclosed and described herein. These drawings are not necessarily in size, but instead the emphasis is on articulating the principles of the invention.

Detailed Description of Embodiments The following detailed description of the present invention will refer to the accompanying drawings showing specific embodiments in which the present invention can be carried out. The embodiments are intended to explain embodiments of the invention in sufficient detail so that those skilled in the art can practice the invention. Other embodiments can be utilized and modified without departing from the scope of the invention. Therefore, the following detailed description should not be construed in a limited sense. The scope of the present invention is defined only by the appended claims and includes the entire scope of the equivalents to which such claims are entitled.

In the present description, the reference to "one embodiment", "an embodiment", or "embodiments" is characterized by one or more of the features of the present invention. Means included in at least one embodiment of. In this description, individual references to "one embodiment," "an embodiment," or "embodiments" necessarily refer to the same embodiment. It is not, nor is it mutually exclusive, unless otherwise stated and / or what is immediately apparent to those skilled in the art from this description. For example, features, structures, operations, and the like described in one embodiment may be included in other embodiments, but are not necessarily included. Accordingly, the art can include various combinations and / or integrations of embodiments described herein.

Embodiments of the present invention relate to annealing systems. Specific embodiments of the present invention relate to industrial microwave heating in which a uniform microwave field and parallel plates are used to control the action of eddy currents on the target substrate 20.

As shown in FIG. 1, the annealing system 10 of the present invention is uniform with a uniform microwave field generator 12, a support element 14, and two relatedly held plates 16 arranged at intervals from each other. It can have two plates 16 and a turntable device 18 configured to rotate the target substrate 20 inside a uniform microwave field in the microwave field generator 12. A set of parallel plates 16 is described herein, but it should be noted that many additional plates are vertical to form a batch reaction (ie, move multiple target substrates at one time). It is possible to stack in.

The target substrate 20 may be a substrate material of any technically known shape such as a semiconductor device, an ion-implanted wafer and / or a silicon wafer, or may have a flat plate or wafer shape. For example, the target substrate 20 may be a semiconductor substrate doped with specific dopant impurities (eg, boron, arsenic, phosphorus) that form a source / drain junction. In some embodiments of the present invention, the target substrate 20 may be a transistor, as schematically shown in FIGS. 2 and 3. Further or instead, the target substrate 20 can include a plurality of target substrates such as a plurality of ion-implanted wafers located between the plates 16 described herein. The annealing process of the target substrate 20 may be used to terminate the activation of the target substrate 20 and repair any associated damage to the injected region, as described in detail below.

The uniform microwave field generator 12 may be a single-mode or multi-mode chamber, or instead, is configured to form a microwave field around and / or between the plates 16 described below. Can include a wave guide port. In some embodiments of the present invention, the range of microwave frequencies generated by the uniform microwave field generator 12 may be in the range of about 900 MHz to 26 GHz. For example, the frequency generated by the microwave field generator 12 may be about 915 MHz, about 2.45 GHz, or about 5.8 GHz or 24 GHz. However, the uniform microwave field generator 12 can be configured to generate any desired microwave frequency without departing from the scope of the present invention. In some embodiments of the invention, the heat generated by the uniform microwave field generator 12 may be in the range of about 400 ° C to 800 ° C. However, other temperatures can be used without departing from the scope of the invention.

The support element 14 can be made of an insulating material such as quartz and can be configured to hold and / or support the plate 16 and the target substrate 20. For example, the support element 14 can be fixed to the rotating element of the turntable device 18. Alternatively, the support element 14 can be attached to the inner wall or other portion of the uniform microwave field generator 12. In addition, the support element 14 may have a slot, clamp, or other configuration that secures the plate 16 and the target substrate 20 to each other at a predefined distance. In some embodiments of the invention, the support element 14 is provided so that different spacing can be used for different plates 16 and / or different target substrates 20 of different shapes and / or different materials. , May be selectively adjustable.

The plates 16 may be substantially parallel to each other and may each include a semiconductor layer 22 and a susceptor layer 24. The susceptor layer 24 can be arranged closest to the target substrate 20, and each of the semiconductor layers 22 at that time is outside the two facing susceptor layers 24. However, in some embodiments of the invention, the susceptor layer 24 can be omitted.

The semiconductor layer 22 can be configured to act as a dielectric at a lower temperature and as a metal at a higher temperature. Therefore, the semiconductor layer 22 has an increased conductivity as the temperature rises, and creates a capacitance type field so as to create a capacitance type electric field plane between the two semiconductor layers 22. Therefore, the plates 16 cooperate to act as parallel plate capacitors. However, in some embodiments of the invention, the surface of a metal or other such conductive material that becomes conductive when the temperature rises, when heated as described herein. The semiconductor layer 22 can instead be replaced with a conductor layer made of such a metal and other materials, as long as it is within the conductive range in which current can flow.

The susceptor layer 24 can be used to preheat the target substrate 20 located between the susceptor layers 24. Specifically, since the susceptor layer 24 can be made of a material configured to absorb microwaves, it cooperates to create a uniform microwave field between the susceptor layers 24. However, in some alternative embodiments of the invention, the susceptor layer 24 is omitted if a uniform microwave field is otherwise created between and / or around the two semiconductor layers 22. Can be done.

The plate 16 can have any technically known size and shape. In some embodiments of the invention, the plate 16 may be disc-shaped, square, or rectangular. In addition, the plate 16 may be a thin flat disc with a thickness generally associated with plates or discs in the solid state industry. The plates 16 can have a distance of about 0.5 mm to about 5 mm from each other. The plate 16 is preferably thin enough to sacrifice structural integrity of the plate 16 when placed on the support element 14 and / or while being heated inside the uniform microwave field generator 12. It can be made as thin as possible. In some embodiments of the invention, the plates 16 can be spaced from about 1 mm to 10 mm. However, other spacing distances can be used without departing from the scope of the invention. Specifically, the plates 16 must be spaced close enough to each other to form a capacitive effect, so surface currents (ie, eddy currents), as described herein. Is close enough to react.

In some embodiments of the invention, the plate 16 can be positioned horizontally, vertically, or in any other direction within a uniform microwave field. The plates 16 can usually be arranged in a direction parallel to each other. However, in some alternative embodiments of the invention, the plates 16 will be relative to each other and / or to the target substrate 20 as long as the plates 16 are close enough to form the capacitive effects described herein. On the other hand, they can be arranged in a non-parallel relationship.

The turntable device 18 may be any technically known mechanism that creates rotation of the members attached to the turntable device 18. For example, the turntable device 18 can include a rotary motor located outside the uniform microwave field generator. Further, one of the above-mentioned support elements 14 can be attached to the rotating shaft of the rotary motor to rotatably support the plate 16 and / or the target substrate 20 at a desired position and at a desired distance from each other. It can extend into the uniform microwave field generator 12. Inside a uniform microwave field, the rotation of the two plates 16 and the target substrate 20 mimics the RF switching of the prior art method, and the polarity of the microwave applied to the two plates 16 and the target substrate 20. Can be changed. For example, the annealing system 10 can be configured so that the rotation of the target substrate 20 can change the polarity of the microwave applied to the target substrate 20 in 15 ° increments. Alternatively, other methods of switching the polarity of the microwave can be used without departing from the scope of the invention.

The turntable device 18 can be configured at any speed that does not cause separation of the plate 16 and / or the target substrate 20. In some embodiments of the invention, the turntable device 18 can rotate the plate 16 and / or the target substrate 20 at a minimum speed of 1 revolution (rpm) per minute and a maximum speed of 10 rpm. For example, the turntable device 18 can rotate the plate 16 and / or the target substrate 20 at a speed of about 2 rpm. However, other speeds can be used without departing from the scope of the invention.

At the time of use, the target substrate 20 is placed between the plates 16 inside the uniform microwave field generator 12 and can be rotated by the turntable device 18 inside the uniform microwave field, so that the target substrate 20 is applied to the target substrate 20. Creates a periodic change in the polarity of the microwave. The target substrate 20 is heated primarily on the basis of its own dielectric properties, converting microwaves into heat and / or creating eddy currents on the surface of the target substrate 20. The eddy current reacts by flowing at right angles to the plate 16 as described below, uniformly heating the target substrate 20. In some embodiments of the invention, it may be essential that the plate 16 be doped to react to a uniform microwave field.

FIG. 4 shows the steps of method 200 for annealing a semiconductor material using a uniform microwave field and parallel plate reaction according to various embodiments of the present invention. The steps of method 200 can be performed in the order shown in FIG. 4 or in a different order. In addition, several steps can be performed simultaneously as opposed to sequential. In addition, some steps cannot be performed. Some of the steps can correspond to a code segment or executable procedure of a computer program, or the application described above.

In some embodiments of the invention, the method 200 can include the step of doping the plate 16 to react to a uniform microwave field, as shown in block 202. For example, room temperature intrinsic silicon may be predominantly microwave transmissive and can be doped to react with a microwave electric field. Doping of the silicone material can change the conductivity at room temperature, allowing microwaves to react to heating / reacting the silicone parallel plate at room temperature. In this embodiment, once the silicone plate is heated, the conductivity of the silicone plate may be reduced based on the bandgap of the non-intrinsic silicon material. FIG. 5 provides graphs showing the bandgap of various materials and their bulk mobility. This reduction in conductivity can achieve microwave reaction / transmission and creates a parallel plate electric field inside the microwave field when the temperature or conductivity is within range. Inside the parallel plate electric field described herein, the eddy currents created by the microwave reaction flow perpendicular or perpendicular to the target substrate 20 (as shown in FIG. 10) and (shown in FIG. 9). As), it will not flow parallel to the surface as in conventional microwave metal reactions.

In some embodiments of the invention, the method 200 determines the distance between the plates 16 based on at least one of the plates and the shape and material used for the target substrate, as shown in block 204. The steps to be adjusted can be selectively included. For example, as mentioned above, the support element 14 is selective so that different spacing can be used for different plates 16 and / or different target substrates 20 of different shapes and / or different materials. It may be adjustable to.

Method 200 can further include placing the target substrate 20 between the plates 16 inside a uniform microwave field (eg, a multimode chamber), as shown in block 206. As described above, the spacing between the plates 16 may be from about 0.5 mm to about 5 mm or 10 mm from each other. As described above, the target substrate 20 and the plate 16 can be floated and supported in the air by a support element 14 made of an insulating material such as quartz.

The method 200 can then include the step of rotating the plate 16 and / or the target substrate 20 inside a uniform microwave field using the turntable device 18, as shown in block 208. It creates a periodic change in the polarity of the microwave applied to the target substrate 20. The target substrate 20 is heated primarily on the basis of its own dielectric properties, converting microwaves into heat and / or creating eddy currents on the surface of the target substrate 20. Conventionally, the surface current or eddy current 26 is formed at the edge or boundary of the flat plate and / or the target substrate 20 inside the microwave field, as shown in FIG. However, the rotating plate configuration disclosed herein results in a flow of eddy currents 26 perpendicular to the target substrate 20 as shown in FIG. 7, and uniform heating of the target substrate 20 as shown in FIG. And selectively heat the defects in the silicon crystal lattice of the target substrate 20. Conversely, conventional heating methods such as the simple microwave heating shown in FIG. 9 do not selectively heat defects inside the silicon crystal lattice.

Specifically, FIG. 8 schematically shows a target substrate 20 provided with a silicon crystal lattice 28 having a defect 30, which is also known as an area of reduced mobility. FIG. 9 shows that the same silicon crystal lattice 28 is independently heated by the microwave 32, and the resulting eddy current 26 flows parallel to the target substrate 20. FIG. 9 also shows the internal heat 34 generated in the silicon crystal lattice 28 by the microwave 32.

FIG. 10 shows that the silicon crystal lattice 28 is heated by the method 200 shown in FIG. 4 described above, and the resulting internal heat 34 is further eddy current flowing at right angles into the target substrate 20. By 26, the defect 30 in the silicon crystal lattice 28 is targeted for volumetric measurement. The directional change of the eddy current 26 allows interfacial polarization to occur at a selection point in the target substrate 20 where the eddy current 26 is suppressed (eg, particle defects, impurities, and other defects 30). The polarization of the defect 30 may not cause a substantial reaction within itself, but the now polarized defect 30 is also exposed to the existing microwave field (eg microwave 32) and the defect 30 is "" Allows heating "selectively". This means that the temperature of the defect 30 is much higher than the rest of the target substrate 20, also referred to herein as bulk material. This bulk material can act as a heat sink and dissipate heat inside the bulk material of the target substrate 20.

Thus, the heating method 200 described herein completed the activation process and injected or doped the target substrate 20 without causing the unwanted thermal runaway and arc of the prior art microwave annealing method. Repair any associated damage to the area. Advantageously, instead of attempting to control, minimize, or eliminate the formation of eddy currents, as in the prior art microwave method, the present invention alters the direction in which the resulting eddy currents flow. , Thereby avoiding non-uniform heating and effectively repairing defects in the target substrate 20.

Although the present invention has been described with reference to the embodiments shown in the accompanying drawings, equivalents can be employed herein and substituted without departing from the scope of the invention described in the claims. Note that you can.

As described above, various embodiments of the present invention have been described, but new ones described in the claims and desired to be protected by a patent certificate include the following.

Claims (19)

An annealing system that anneals the target substrate
A uniform microwave field generator configured to generate a uniform microwave field,
Two plates spaced apart from each other inside the uniform microwave field generator and arranged in a direction to form a capacitance effect between themselves inside the uniform microwave field.
Inside the uniform microwave field, the two plates and the target substrate arranged between the two plates are rotated, thereby applying microwaves from the uniform microwave field to the target substrate. With a turntable device, which is configured to create a periodic change in polarity of the
An annealing system in which a plurality of sets of the two plates are stacked in the axial direction of the rotation axis of the turntable device . The annealing system according to claim 1, wherein the two plates are doped so as to react with the uniform microwave field generated by the uniform microwave field generator. The support element according to claim 1 or 2, further comprising a support element including an insulating material, wherein the turntable device is attached to the two plates and the two plates are held in parallel with each other. Annealing system. The annealing system according to claim 3, wherein at least one of the support elements is configured to fix the target substrate between the two plates in parallel with the two plates. The annealing system according to claim 3 or 4, wherein the support element is selectively adjustable so that the distance between the two plates can be adjusted. The annealing system according to any one of claims 1 to 5, wherein the two plates are arranged at intervals of 0.5 mm to 10 mm. Claims 1 to 6 that the eddy current in the uniform microwave field reacts to the periodic change of the polarity by flowing at right angles to the two plates, resulting in uniform heating of the target substrate. The annealing system according to any one of the above. Any one of claims 1 to 7, wherein the two plates have sufficiently high conductivity to form an electric field in the uniform microwave field and heat resistance from 400 degrees Celsius to 800 degrees Celsius. Annealing system described in. The uniform microwave field generator is a single-mode or multi-mode chamber, or a wave guide port configured to form the uniform microwave field around the two plates. The annealing system according to any one of the above. The annealing system according to any one of claims 1 to 9, wherein the uniform microwave field generator generates a frequency in the range of 900 MHz to 26 GHz. Each of the two plates includes a semiconductor layer and a susceptor layer, and the two plates are arranged so that the susceptor layers face each other. Any one of claims 1 to 10. Annealing system described in section. The annealing system according to any one of claims 1 to 11, wherein each of the two plates includes a semiconductor material or a conductor material configured so that the conductivity increases with increasing temperature. A method of annealing semiconductor materials
A target substrate containing the semiconductor material is placed between two plates inside a uniform microwave field.
Including creating a periodic change in the polarity of the microwave applied to the target substrate from the uniform microwave field.
The periodic change results in a flow of eddy currents perpendicular to the target substrate and the two plates .
The step of creating the periodic change is to rotate the two plates and the target substrate inside the uniform microwave field, and as a result, the period of polarity of the microwave applied to the target substrate. Including the occurrence of changes
A method in which a plurality of sets of the two plates are stacked in the axial direction of a rotation axis that rotates the plurality of sets of the two plates and the target substrate . Further, the doping comprises doping the two plates before placing the target substrate between the two plates, the doping being sufficient to cause the two plates to react to the uniform microwave field. The method according to claim 13 . The method of claim 13 or 14 , wherein the target substrate comprises the semiconductor material doped with impurities. Furthermore, based on the shape and materials used for at least one and said target substrate of said two plates, one of claims 13 to 15 comprising adjusting the distance of said two plates The method according to item 1. The method according to any one of claims 13 to 16 , wherein the uniform microwave field includes frequencies in the range of 900 MHz to 26 GHz. A method of annealing semiconductor materials
Doping the parallel plates, said doping is sufficient to cause the parallel plates to react to a uniform microwave field.
A target substrate is placed between the parallel plates inside the uniform microwave field.
Rotating the parallel plate and the target substrate inside the uniform microwave field, thereby creating a periodic change in the polarity of the microwave applied to the target substrate from the uniform microwave field. Including
The target substrate contains the semiconductor material doped with impurities.
The uniform microwave field includes frequencies in the range 900 MHz to 26 GHz.
The parallel plates are spaced close enough to each other to form a capacitive effect between the parallel plates inside the uniform microwave field.
The periodic change results in a flow of eddy currents perpendicular to the target substrate and the parallel plate, resulting in uniform heating of the target substrate and selectively heating defects in the target substrate .
A method in which a plurality of sets of the parallel plates are stacked in the axial direction of a rotation axis for rotating the plurality of sets of parallel plates and the target substrate . 18. The method of claim 18 , wherein the rotation is performed at a speed in the range of 1 revolution per minute to 10 revolutions per minute.