Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate
Reexamination Certificate
2000-11-02
2002-10-01
Everhart, Caridad (Department: 2825)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Reexamination Certificate
active
06458672
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of substrates. More particularly, the invention provides a technique including a method and device for cleaving a substrate in the fabrication of a silicon-on-insulator substrate for semiconductor integrated circuits, for example. But it will be recognized that the invention has a wider range of applicability; it can also be applied to other substrates for multi-layered integrated circuit devices, three-dimensional packaging of integrated semiconductor devices, photonic devices, piezoelectronic devices, microelectromechanical systems (“MEMS”), sensors, actuators, solar cells, flat panel displays (e.g., LCD, AMLCD), biological and biomedical devices, and the like.
Craftsmen or more properly 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. A common example 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 upon a rotating blade or tool, which cuts through 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 diamond or glass.
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 is directed preferentially along a crystallographic plane of a diamond material. This 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 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 or household glass, they have severe limitations in the fabrication of small complex structures or precision workpieces. 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.
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.
SUMMARY OF THE INVENTION
According to the present invention, an improved technique for removing a thin film of material from a substrate using a controlled cleaving action is provided. This technique allows an initiation of a cleaving process on a substrate using a single or multiple cleave region(s) through the use of controlled energy (e.g., spatial distribution) and selected conditions to allow an initiation of a cleave front(s) and to allow it to propagate through the substrate to remove a thin film of material from the substrate. In an exemplary embodiment, the present invention provides a “beta” annealing process before the controlled cleaving action to improve the quality of detached surfaces.
In a specific embodiment, the present invention provides a process for forming a film of material from a donor substrate using a controlled cleaving process. The process includes a step of introducing energetic particles (e.g., charged or neutral molecules, atoms, or electrons having sufficient kinetic energy) through a surface of a donor substrate to a selected depth underneath the surface, where the particles are at a relatively high concentration to define a thickness of donor substrate material (e.g., thin film of detachable material) above the selected depth. To cleave the donor substrate material, the method provides energy to a selected region of the donor substrate to initiate a controlled cleaving action in the donor substrate, whereupon the cleaving action is made using a propagating cleave front(s) to free the donor material from a remaining portion of the donor substrate. In preferred embodiments, a beta annealing step precedes the initiation of the controlled cleaving action. The beta annealing step can occur during the introduction of energetic particles or after such introduction of particles or immediately before a cleaving process, and other times.
In an alternative embodiment, the present invention provides a process for forming a silicon-on-insulator substrate using a controlled cleaving technique. The present process includes steps of providing a donor substrate and introducing particles (e.g., charged or neutral molecules, atoms, or electrons having sufficient kinetic energy) through a surface of the donor substrate to a selected depth underneath the surface. The particles are at a concentration at the selected depth to define a thickness of substrate material (e.g., thin film of material) to be removed above the selected depth. The multi-layered silicon-on-insulator structure is formed by joining the donor substrate to a target substrate such that the surface of the donor substrate faces a face of the target substrate. A controlled cleaving action to free the thin film of material occurs by providing energy to a selected region of the combined substrate structure to initiate the controlled cleaving action at the selected depth in the substrate, whereupon the cleaving action is made using a propagating cleave front to free a portion of the material to be removed from the substrate. In some embodiments, the step of providing energy sustains the controlled cleaving action to remove the material from the substrate to provide the thin film of material.
Alternatively, the method uses an additional step(s) of providing additional energy to the substrate to sustain the controlled cleaving action to remove the material from the substrate to provide the film of material. The resulting substrate is the silicon-on-insulator structure. In preferred embodiments, a beta annealing step precedes the initiation of the controlled cleaving action.
In most of the embodiments, a cleave is initiated by subjecting the material with sufficient energy to fracture the material in one region, causing a cleave front, without uncontrolled shattering or cracking. The cleave front formation energy (E
c
) must often be made lower than the bulk material fracture energy (E
mat
) at each region to avoid shattering or cracking the material. The directional energy impulse vector in diamond cutting or the scribe line in glass cutting are, for example, the means in which the cleave energy is reduced to allow the controlled creation and propa
Cheung Nathan W.
Henley Francois J.
Everhart Caridad
Lee Calvin
Silicon Genesis Corporation
Townsend & Townsend & Crew LLP
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