Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Physical deformation
Reexamination Certificate
2001-01-08
2004-04-20
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Physical deformation
C257S513000, C257S301000, C257S353000, C257S417000, C257S418000, C257S419000, C438S050000, C438S053000
Reexamination Certificate
active
06724058
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for producing a filled recess in a material layer, and to an integrated circuit configuration produced by the method.
There are a large number of integrated circuit configurations for which it is advantageous to have a recess with dimensions of at least a few &mgr;m.
By way of example, such a circuit configuration encompasses a CMOS microphone in which a recess forms a cavity, the so-called rear volume, above which a diaphragm is disposed that is made to oscillate by sound waves. A capacitor is used to convert the oscillations into electrical signals. The greater the volume of the recess, the easier it is for the diaphragm to oscillate and the lower the sound levels that can be detected. For microphones, it is accordingly desirable to provide as deep a recess as possible having a large horizontal cross section.
The reference by P. R. Scheeper et al., titled “A Review of Silicon Microphones”, Sensors and Actuators A 44 1994, pages 1 to 11, describes a first microphone, in which a recess serving as rear volume is produced in a first silicon substrate. In a second silicon substrate, a perforated cover layer and, above that, a diaphragm is produced. The first silicon substrate is connected to the second silicon substrate. A capacitance is formed by the cover layer and the first silicon substrate. Since the recess and the cover layer are produced in separate substrates, the process complexity is very high. Connecting the substrates requires high temperatures, which can impair the process reliability.
These disadvantages are avoided in a second microphone described in the aforementioned patent application. The cover layer and the recess are produced in a single substrate. To this end, the recess is filled with a sacrificial layer. A perforated cover layer is produced above the sacrificial layer, and a diaphragm is produced above this perforated cover layer. The sacrificial layer is then removed through an opening at the edge of the diaphragm by etching.
If a circular plane whose diameter is equivalent to at least the depth of a recess fits into a horizontal cross section of the recess, then the thickness of a conformally deposited layer must be at least the depth of the recess for the recess to be filled by the layer. In the case of microphones, the associated recesses usually have the dimension described.
In general, however, deposition of a layer thicker than a few &mgr;m results in the layer peeling off or in the formation of cracks in the layer. Furthermore, the circuit configuration in question can become buckled on account of stresses in a layer. Not least, depositing a thick layer requires a high input of time and cost. Hence, recesses that are filled at some time or other have dimensions below a few &mgr;m in the prior art.
Since, in the second microphone, the recess is filled during the production method by depositing the sacrificial layer, it is shallow, in contrast to the recess in the first microphone. The rear volume of the second microphone is correspondingly smaller than in the first microphone.
Other integrated circuit configurations for which it is advantageous to have a recess with dimensions of at least a few Mm encompass, by way of example, micromechanical components such as rotation rate sensors or acceleration sensors, which have moving structures which are disposed in cavities and for which attempts are made to obtain the greatest possible freedom of movement. Published, Non-Prosecuted German Patent Application DE 195 09 868 A1 describes a production method for such micromechanical components. On a substrate, a bottom sacrificial layer is produced, and a structure layer is produced above this and is patterned, which produces a structure surrounded by a recess. The recess is filled by depositing a top sacrificial layer, above which a cover layer is applied. Etching holes in the cover layer are used to remove the sacrificial layers, and the recess forms part of a cavity in which the structure can move.
In the case of the acceleration sensor or the rotation rate sensor, vibration or rotation is detected using the structure, which can be made to oscillate laterally. The cover layer serves to protect the circuit configuration. The sensitivity of the acceleration sensor or of the rotation rate sensor is higher the thicker the structure, i.e. the deeper the recess.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for producing a filled recess in a material layer, and an integrated circuit configuration produced by the method that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which a filled recess having a depth of at least a few &mgr;m can be produced in a material layer, the recess having a horizontal cross section in which at least one circular plane with a diameter of a few &mgr;m fits.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for producing a filled recess. The method includes providing a material layer, and removing a portion of the material layer in a region provided for a recess to be created until a bottom of the recess is exposed, thereby creating a first trench having a horizontal cross-section being smaller than the recess. A first filling layer is deposited substantially conformally and has a depth that is less than approximately half of a depth of the recess in an area where the portion of the material layer has been removed for forming a first structure forming part of a filling of the recess. A remaining portion of the material layer in the region is removed resulting in a second trench having a horizontal cross-section being smaller than the recess to be created. A second filling layer is deposited substantially conformally and has a depth that is less than approximately half of the depth of the recess for forming a second structure in an area where the remaining portion of the material layer in the region has been removed and the second structure forms a further part of the filling of the recess. The second structure is laterally adjacent the first structure.
In the method according to the invention, at least one first structure and at least one second structure are produced in a region provided for the recess. The structures adjoin one another at the sides and form a filling in the recess, and each of the parts of the structures have respectively opposite side parts whose distance from one another is shorter than approximately half of a depth of the recess. The recess is not, as in the prior art, produced first and then filled in one step, which is the reason why the deposition of a thick layer with all its disadvantages is avoided. The method according to the invention permits the production of filled deep recesses having large horizontal cross sections.
Such a method is advantageous for any technical field in which recesses are filled by essentially conformal layers. Such a field is semiconductor process technology, for example.
The described dimensions of the first structure and of the second structure permit the structures to be produced by method steps which are independent of the depth of the recess.
To produce the first structure, at least one narrow recess is first produced in a region, which is provided for the recess, of the material layer by removing a portion of the material layer. The narrow recess has a smaller horizontal cross section than the recess to be produced and forms part of the recess to be produced. Next, side-forming layered parts of the first structure are produced which are thickened at the sides until the parts meet one another and thereby form the first structure. A boundary between the abutting parts is therefore situated inside the first structure. The first structure is produced either in the narrow recess or outside the narrow recess. The second structure is produced by first producing side-forming layered parts of the second structure which are thickened at the sides u
Aigner Robert
Oppermann Klaus-Günter
Greenberg Laurence A.
Infineon - Technologies AG
Jackson Jerome
Locher Ralph E.
Nguyen Joseph
LandOfFree
Method for producing a filled recess in a material layer,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for producing a filled recess in a material layer,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for producing a filled recess in a material layer,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3219517