Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Reexamination Certificate
1999-06-17
2001-09-18
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
C438S460000
Reexamination Certificate
active
06291326
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 multi-layered 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, microclectromechanical 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 useftil 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 including devices (e.g., transistors, capacitors, resistors, inductors) 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 a specific embodiment, the present invention provides a process for forming a novel substrate material. The substrate material is generally a blank wafer or donor wafer without any active devices thereon. The substrate material is implanted using a plurality of particles. That is, 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. The implanted substrate is a patterned implant, which can be used in a subsequent separation process. Alternatively, the present process includes forming a stressed region on the donor substrate at a selected depth underneath a surface of the substrate, where a thickness of donor substrate material (e.g., thin film of detachable material) above the selected depth is defined. Before separation, however, the substrate is processed using conventional semiconductor process steps including those requiring high temperatures to form active devices on the substrate. After the active devices are formed, the film of material having devices from the donor substrate is separated using a controlled cleaving process. To cleave the donor substrate material, energy is applied 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 an alternative specific embodiment, the present invention provides a novel substrate material, which is implanted before semiconductor processing to fabricate devices. The present substrate has a plurality of particles defined in a pattern in the substrate at a selected depth underneath the surface of the substrate. The particles are at a concentration at the selected depth to define a substrate material to be removed in a later cleaving process above the selected depth. The substrate material is removed after forming active devices on the substrate material using, for example, conventional semiconductor processing techniques. The pattern is defined in a manner to substantially prevent a possibility of detachment of the substrate material to be removed during conventional thermal processes of greater than about room temperature or greater than about 200 degrees Celsius or greater than about 400 degrees Celsius. The substrate is cleaved using, for example, a controlled cleaving process by way of a pressurized fluid or the like, which will be described in more detail below. Alternatively, the process includes forming a stressed region in the substrate material at a selected depth underneath a surface of the substrate, where a thickness of donor substrate material (e.g., thin film of detachable material) above the selected depth is defined for separation.
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, fo
Cheung Nathan W.
Henley Francois J.
Le Dung Anh
Nelms David
Silicon Genesis Corporation
Townsend and Townsend / and Crew LLP
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