Patent Application
20050150597
1. Field of the Invention
The field of the invention relates to the manufacture of substrates. More specifically, embodiments of the present invention relate to an apparatus and method for controlled cleaving.
2. Related Art
Crafts people have been building useful articles, tools or devices using less useful materials for numerous years. In some cases, articles are assembled by way of smaller elements or building blocks. Alternatively, less useful articles are separated into smaller pieces to improve their utility. Examples of these articles to be separated include substrate structures such as a glass plate, a diamond, a semiconductor substrate, and others.
These substrate structures are often cleaved or separated using a variety of techniques. In some cases, the substrates can be cleaved using a saw operation. The saw operation generally relies on a rotating blade or tool, which cuts the substrate material to separate the substrate material into two pieces. This technique, however, is often extremely rough and cannot generally be used for providing precision separations in the substrate for the manufacture of fine tools and assemblies. Additionally, the saw operation often has difficulty separating or cutting extremely hard and/or brittle materials such as glass or diamond.
Accordingly, techniques have been developed to separate these hard and/or brittle materials using cleaving approaches. In diamond cutting, for example, an intense directional thermal/mechanical impulse generally causes a cleave front to propagate along major crystallographic planes, where cleaving occurs when an energy level from the thermal/mechanical impulse exceeds the fracture energy level along the chosen crystallographic plane.
In glass cutting, a scribe line using a tool is often impressed in a preferred direction on the glass material, which is generally amorphous in character. The scribe line causes a higher stress area surrounding the amorphous glass material. Mechanical force is placed on each side of the scribe line, which increases the stress along the scribe line until the glass material fractures, preferably along the scribe line. This fracture completes the cleaving process of the glass, which can be used in a variety of applications including households.
Although the techniques described above are satisfactory for the most part, as applied to cutting diamonds and glass material, they have severe limitations in the fabrication of small complex structures or precision work-pieces. For instance, the above techniques are often “rough” and cannot be used with great precision in fabrication of small and delicate machine tools, electronic devices, or the like. Additionally, the above techniques may be useful for separating one large plane of glass from another, but are often ineffective for splitting off, shaving, or stripping a thin film of material from a larger substrate. Furthermore, the above techniques may often cause more than one cleave front, which join along slightly different planes, which is highly undesirable for precision cutting applications. Other processing techniques such as using a release layer have had limited success. Such release layer techniques often require wet chemical etching, which is often undesirable in many state of art applications.
For instance, the semiconductor industry has attempted to improve upon conventional cleaving techniques to aid in the manufacturing of small electronic devices. In particular, a controlled cleaving process for separating layers of substrate material was desired and as a result, many new designs and processes have been provided. For example, a blade or knife device has been used to initiate cleaving between wafer layers. Prior Art
Although often satisfactory, using a blade for the initiating process can result in some deleterious conditions. For example, many cleaving processes leave the cleaved wafer surfaces with a limited roughness and with loose particles that were broken during the cleaving operation. Under these conditions, surface damage can occur if the cleaved surfaces are allowed to contact each other after separation.
Prior Art
From the above, it is seen that a technique for separating a thin film of material from a substrate which is cost effective and efficient is often desirable.
Accordingly, the present invention provides an improved technique for removing a thin film of material from a bonded substrate using a controlled cleaving action. This technique allows an initiation of a cleaving process on a bonded substrate through the use of controlled energy and selected conditions to allow it to propagate through the substrate to remove a thin film of material from the substrate. The initiation of the cleaving process first applies a tensile force at the edge of a bonded (e.g., composite) substrate, and then an initiation force is applied between the substrate that initiates a cleaved region on a substrate. During cleaving there are at least two phases of separation. The first phase is the initiation and the second phase is the propagation of the cleave front. This two phase separation sequence is controlled through programmed acceleration and velocity profiles of separation distance of the substrate edges. In addition, the present invention provides a cleaving apparatus and method that does not allow the thin film to contact the composite substrate after cleaving, thus reducing deleterious effects such as scratching.
An apparatus and method for controlled cleaving is presented. Embodiments of the present invention include an apparatus for cleaving a bonded substrate comprising a bottom shell coupled to a hinge mechanism, a top shell coupled to the hinge mechanism, a plurality of o-rings or suction cups coupled to the top and bottom shells for providing a suction force sufficient to exert a tensile force to the top and bottom of a substrate. One embodiment for initiation is a compliant member for sealing a portion of a grove edge of a bonded substrate and for maintaining a pressure inside a volume formed between the groove edge and the groove edge of the substrate, a gas port for supplying gas to the volume, and a height adjustment mechanism coupled to the top shell and the bottom shell for separating the top shell from the bottom shell. In another embodiment of the invention, a blade edge is used to initiate propagation.
Embodiments of the present invention also include a method for initiating and cleaving a bonded substrate comprising of placing the bonded substrate on the bottom cleaving shell, then placing the top cleaving shell on the other side of the bonded substrate, the substrate comprising a first perimeter edge and a second perimeter edge, to compress and seal a compliant member against the first perimeter edge and the second perimeter edge of the substrate to form a selected volume, pressurizing the selected volume with a gas, wherein the gas is at a pressure capable of initiating a cleave front in the substrate, and providing a separating force substantially perpendicular to the cleave front. In addition, tensile forces are also applied from vacuum to the top and bottom shells to maintain separation of the cleave which prevents the substrate from touching after cleaving. In another embodiment of the invention, a blade edge is used to initiate propagation. In this embodiment of the invention, an electrically controlled motor coupled to a hinge mechanism controls the acceleration and velocity of the cleave front across the substrate.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiments, which are illustrated in the various drawing figures.
The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Prior Art
Prior Art
a is an illustration of an exemplary apparatus in a closed position for controlled cleaving in accordance with embodiments of the present invention.
b is an illustration of an exemplary apparatus in an open position for controlled cleaving in accordance with embodiments of the present invention.
Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
Some portions of the detailed descriptions that follow are presented in terms of procedures, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. A procedure, logic block, process, etc., is here, and generally, conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, bytes, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present invention, discussions utilizing terms such as “sensing,” “controlling,” “scanning,” “receiving,” “sending,” “sensing,” “monitoring,” or the like, refer to the action and processes (e.g., processes 900 and 1100) of a computer system or similar intelligent electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
U.S. Pat. Nos. 6,155,909, 6,221,740, 6,23,941, 5,994,207, 6,013,567, 6,013563, 6,033,974, 6,284,631, 6,291,313 are incorporated herein by reference as foundation for the present invention.
Referring now to
Computer system 12 includes an address/data bus 10 for communicating information, a central processor 1 coupled with bus 10 for processing information and instructions, a volatile memory unit 2 (e.g., random access memory, static RAM, dynamic RAM, etc.) coupled with bus 10 for storing information and instructions for central processor 1 and a non-volatile memory unit 3 (e.g., read only memory, programmable ROM, flash memory, EPROM, EEPROM, etc.) coupled with bus 10 for storing static information and instructions for processor 1. Computer system 12 may also contain an optional display device 5 coupled to bus 10 for displaying information to the computer user. Moreover, computer system 12 also includes a data storage device 4 (e.g., disk drive) for storing information and instructions.
Also included in computer system 12 of
An o-ring (e.g., suction cup) 315 forms a seal around a portion of the perimeter edges of the composite substrate 400. It is appreciated that the o-ring 315 may also be a suction cup device and may also use a vacuum force to provide suction. The o-ring is hollow and operates at ambient (atmospheric) pressure to provide compliance, but could be sealed and pressurized to control the compliance and sealing force, or could be solid. A gas port 330, in this case, formed by a needle extending through o-ring 315, provides a burst, bursts or a steady flow of gas to a perimeter plenum formed by the sealed edge groove of the composite substrate. The o-ring 315 does not have to seal the entire perimeter of the composite substrate, such as if the composite substrate has an alignment feature such as a flat side or sides.
Gas is provided from a gas source 325, such as a dry nitrogen source, but could be other types of gas such as air, helium, or argon. The gas flow is controlled by a solenoid valve 390, or similar valve, that is coupled to a control module 12 which controls the gas supplied to the gas port 330. In one embodiment of the present invention, the gas source provides gas at a nominal pressure of about 300 PSI (pounds per square inch). In one embodiment of the invention, the pressure can be upwards of 3,000 PSI. The burst of gas is usually sufficient to initiate cleaving between the composite substrate. Gas may be lost through leakage between the o-ring and the substrate, especially where the o-ring does not form a seal with the substrate. Beneficially, gas loss increases as cleaving propagates across the substrate plane. The gas loss allows for a controlled cleave process that does not propagate too quickly, and in addition, cleaving stops when the pressure drops below the point to continue propagation. The pressure loss can be monitored and controlled by the control module 12. Control module 12 controls the gas solenoid 390 and monitors the gas loss between the o-ring and the substrate. To aid in controlling the cleave process, the control module 12 turns off the gas supply when a predetermined pressure loss is detected.
A lifting mechanism 309 is included to provide a tensile force to the composite substrate and for separating the layers after the cleaving process is completed. Lifting mechanism 309 can be a stepper motor that controls a screw shaft 308 or any other comparable mechanism suitable for separating the composite substrate after cleaving and for providing a tensile force during the cleaving process, for example, a servo motor or any other electrically controlled motor device. A connecting member 307 connects the top lid 301 and the bottom support to the screw shaft 308. In one embodiment of the present invention, when the stepper motor 309 turns the screw shaft 308, the top and bottom begin to separate from each other, thus providing tensile force to the composite substrate 400. In one embodiment of the invention, a hinge mechanism is used in conjunction with an electrically controlled motor to provide the tensile force used to separate the substrate 400. Examples of the hinge mechanism and electrically controlled motor are illustrated and described in
A height adjustment mechanism 309 is provided to accurately align the gas port 330 with the edge groove/plenum. In addition, the height adjustment mechanism 309 applies a tensile force to the composite substrate and ensures the wafers do not contact each other after cleaving. The height adjustment mechanism 309 moves along with the gas port 330 and tubing, relative to the top/base of the cleave tool, as represented by the arrows 260. Alignment accuracy is achieved with a stepper motor that can be controlled with a control module, such as control module 12 of
Next, in step 285, vacuum is applied to an o-ring as to allow the height adjustment mechanism to apply a tensile force to the substrate. Next, a burst of gas is applied to a region on the perimeter of the substrate in step 286. Once cleaving has initiated, the height adjustment slowly lifts the top wafer from the bottom wafer substrate. By applying the tensile force in step 285, the wafers do not come in contact again after cleaving has been completed. If the substrate cleaving tool has a cleave indicator, the substrate is then checked for completion of the cleave in step 288. If the cleave is complete, the process can stop in step 290). If the cleave is not complete, another burst of gas may be applied. The subsequent burst of gas may be of the same duration and pressure, or of a different duration and/or pressure than the initial burst of gas. It is noted that some substrates are easier to cleave than others, depending on the type of material and pre-cleave treatment (e.g. implant species, dosage, and energy), and that some cleave processes may be consistent and reliable enough to be performed without a cleave indicator.
This provides a differential pressure across the substrate. A differential pressure is desirable because of the nature of cleave initiation and propagation. In most materials of interest, cleaving is essentially a stressed fracture. The energy required to initiate such a fracture may be lowered by providing a local mechanical defect, such as a crack or scratch. Thus, once the cleave is initiated in the low pressure region (near the gas port), higher pressure may be applied to the substrate to keep the cleaved halves from “jumping” and potentially breaking across the face of the half. A sensor, represented by circle 518, is placed near the flat of the substrate to determine if the cleave has propagated through the substrate, as discussed above. Alternatively, a constant pressure may be applied, depending on the type of material(s) the substrate is made of, the thickness of the cleaved halves, and the pressure and duration of the gas being applied, and other factors.
A pressure gradient may be important to prevent some composite substrates from flying apart and breaking when cleaved, while allowing cleaving to form and propagate. It is believed the combination of the applied pressure gradient and the compliant pad in the top and bottom shells allow the efficient cleaving of composite substrates while avoiding breakage, especially of the donor substrate. It is recognized that other combinations of compliant pads and pressures may obtain similar results, and that different pressures and pressure gradients may be appropriate for different materials or cleave conditions. Similarly, the force may be applied between the top shell and the bottom shell by a variety of mechanisms, such as pre-set springs, weights, gas or hydraulic cylinders, or even a compliant pad with a graded durometer, the durometer being less near the gas port, where the cleave is initiated.
Although the above injector has been described in terms of tubing, it an also be may other means for supplying gas and/or fluid to the system. Here, the means can include, among others, almost any suitable member that directs fluid into the system. The member can be shaped in a variety of configurations such as a rectangle, a semicircle, or other shape, which is suitable for directing the fluid into the system. The end of the means can be flared, pointed, or any other shape suitable for supplying the fluid. One of ordinary skill in the art would recognize many other variations, alternatives, and modifications.
a is an illustration of an exemplary cleaving apparatus 1000a for controlling cleaving in a closed position in accordance with embodiments of the present invention. The cleaving apparatus 1000a uses an electrically controlled motor 1004 to control the position of the movable top 1002 in relation to the position of the fixed bottom 1003. In one embodiment of the invention, the top 1002 pivots at the electrically controlled motor 1004 to propagate a cleave between a top layer 304 and a bottom layer 305 of a substrate. In one embodiment of the invention, a cleave initiation device 1008 is used to initiate a cleave 400 in the substrate. In one embodiment of the invention, a blade 1010 is used to strike the substrate approximately parallel to the planar surface of the substrate. Suction cups 1006 couple the substrate to the top 1002 and bottom 1003 of the cleaving apparatus 1000a and provide a tensile force to separate the layers 304 and 305 of the substrate.
After the cleave is initiated, the electrically controlled motor 1004 provides a force to pivot the top 1002 and provides a tensile force to the top 304 and bottom 305 of the substrate to propagate the cleave across the planar surface of the substrate. In one embodiment of the invention, the acceleration and velocity of the cleave front can be controlled by the electrically controlled motor 1004. In one embodiment of the invention, a computer or logic controller provides movement instructions to the motor 1004. In this embodiment of the invention, a cleave position sensor and/or force sensor can be used to determine the position, velocity and acceleration of the cleave front which is used to control the motor 1004. In another embodiment of the invention, the position of the cleave front can be determined from the angle between the top 1002 and the bottom 1003 at the electrically controlled motor 1004.
b is an illustration of an exemplary cleaving apparatus 1000b in an open position in accordance with embodiments of the present invention.
Above, a process for non-contact cleaving is presented. In an alternate embodiment of the present invention, a contact cleaving process is used to initiate cleaving in a substrate. In one embodiment of the invention, striking the substrate with a blade, for example initiates cleaving in the substrate.
Process 1100 comprises step 1102, initiating a cleave in a substrate comprising a planar surface by striking along a portion of an edge of the substrate substantially parallel to the planar surface under tensile force. In one embodiment, a blade is struck against the edge of the substrate to initiate the cleave.
Step 1104 comprises propagating the cleave by controlling acceleration and velocity of the cleave across the planar surface, wherein propagating the cleave frees a portion of the substrate to be removed. In one embodiment of the invention, suction cups are used to provide a tensile force on the substrate during the cleaving.
Step 1106 comprises separating the substrate into layers by maintaining the applied tensile force, wherein after the substrate is cleaved, the layers do not touch. By not allowing the surfaces form contacting after cleaving, surface finish is greatly improved.
Embodiments of the present invention, an apparatus and method for cleaving have been described. While the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the following Claims.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
