Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
1999-05-04
2004-06-29
Chen, Kin-Chan (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
C156S345420
Reexamination Certificate
active
06756316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to integrated circuits and, more particularly, to pressure transducer structures and efficient methods for fabricating the same.
2. Description of the Related Art
Pressure transducers are devices that are typically fabricated into semiconductor devices to sense external pressure conditions. In some applications, pressure transducers are coupled to integrated control circuitry that may be triggered to perform an operation in response to the sensed external pressures.
For ease of understanding,
FIG. 1A
shows a cross-sectional view of a pressure transducer structure
100
. The pressure transducer structure
100
is fabricated over a substrate
102
. The substrate
102
has an inter-metal oxide
104
formed thereon, and a patterned metallization layer
108
formed over the inter-metal oxide
104
. An inter-metal oxide
106
is then formed over the patterned metallization layer
108
and portions of the inter-metal oxide layer
104
. During the fabrication process, a hole
114
is etched into the inter-metal oxide layer
106
to define a cavity having a bottom surface that is the patterned metallization layer
108
.
Once the hole
114
is defined, a sacrificial oxide material is deposited into the hole
114
before a patterned metallization layer
110
is formed over the inter-metal oxide layer
106
. Conventionally, the sacrificial oxide material is deposited into the hole
114
to provide mechanical support for the subsequently formed patterned metallization layer
110
. However, the sacrificial oxide material must be removed from the hole
114
before an oxide layer
112
is deposited over the inter-metal oxide layer
106
and the patterned metallization layer
110
.
As shown in
FIG. 1B
, a portion of the hole
114
is left exposed once the patterned metallization layer
110
is formed over the inter-metal oxide layer
106
to enable a wet etch chemical to come into contact with the sacrificial oxide (i.e., that is contained in the hole
114
). Once all of the sacrificial oxide is removed from the hole
114
, the oxide layer
112
is deposited over the inter-metal oxide layer
106
and the patterned metallization layer
110
. At this point, the pressure transducer structure
100
is complete, and a voltage may be measured between the patterned metallization layer
108
and the patterned metallization layer
110
to determine an external pressure.
In this example, a pressure P
1
is shown applied to the oxide layer
112
that lies over the hole
114
. In pressure transducers, the pressure P
1
may be determined by measuring the capacitance C
1
detected between the patterned metallization layers
108
and
110
. When the pressure increases by &Dgr;P as shown in
FIG. 1C
, the patterned metallization layer
110
and the oxide layer
112
will compress into the hole
114
. When this happens, the capacitance C
1
of
FIG. 1A
will change to a capacitance C
2
, which is measured between the patterned metallization layers
108
and
110
. By measuring the new capacitance value, it is possible to accurately determine the new increased external pressure.
Although these conventional pressure transducer structures
100
find many practical applications in devices, such as, altitude sensors, flow meters, accelerometers for deploying airbags in automobiles, and other useful applications, they unfortunately add substantial manufacturing complexities to standard CMOS circuitry manufacturing.
Thus, in order to manufacture conventional pressure transducers, an additional level of manufacturing must be completed after the interconnecting contact structures are formed. For example, once the interconnecting structures are formed, an additional application of photoresist must be applied and patterned to define the location of the hole for the pressure transducer. Once the photoresist mask is formed, the pressure transducer hole is etched and filled with the sacrificial oxide. Next, the excess sacrificial oxide may be removed with a chemical mechanical polishing operation before the patterned metallization layer
110
is applied. Next, the sacrificial oxide is removed with the wet etching process before the oxide layer
112
is applied. As can be appreciated, the process of integrating pressure transducers into standard CMOS circuitry manufacturing is a task that increases complexity and adds a substantial amount of cost to CMOS fabrication operations.
In view of the foregoing, there is a need for a method and apparatus for manufacturing integrated circuit devices that include pressure transducer structures, without increasing manufacturing complexity.
SUMMARY OF THE INVENTION
Broadly speaking, the present invention fills these needs by providing a pressure transducer structure that may be efficiently made using standard CMOS manufacturing operations that avoid introducing added manufacturing complexities and increased costs. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.
In one embodiment, a method for making a semiconductor pressure transducer structure is disclosed. The method includes patterning a first metallization layer that lies over an first oxide layer to produce a first patterned metallization layer that is not in electrical contact with a substrate. Forming a tungsten plug in a second oxide layer that overlies the first patterned metallization layer, such that the tungsten plug is in electrical contact with the first patterned metallization layer. Patterning a second metallization layer that overlies the first patterned metallization layer and the tungsten plug to produce a second patterned metallization layer. The patterning of the second metallization layer is configured to prevent the second patterned metallization layer from completely overlying the tungsten plug. The method further includes submerging the pressure transducer structure in a basic solution having a pH level that is about greater than 7. In this manner, the tungsten plug will come in direct contact with the basic solution that causes the tungsten plug to be removed while the pressure transducer structure is submerged in the basic solution.
In another embodiment, a system for making an air capacitive hole for a pressure transducer structure is disclosed. The air capacitive hole lies between a bottom metallization feature and a top metallization feature. The system for making the air capacitive hole includes plasma etching a bottom metallization layer to form the bottom metallization feature that is not in electrical contact with a substrate. Forming a dielectric layer over the bottom metallization feature. The dielectric layer having a tungsten plug that is in contact with the bottom metallization feature. Plasma etching a top metallization layer to form the top metallization feature that substantially overlies the tungsten plug, but leaves an opening down to the tungsten plug. The system further includes submerging the pressure transducer structure in a basic solution. In this manner, the tungsten plug will come in direct contact with the basic solution that causes the tungsten plug to erode and define the air capacitive hole while the pressure transducer structure is submerged in the basic solution.
In yet another embodiment, an apparatus for making an air capacitive hole used in a semiconductor pressure transducer structure is disclosed. The air capacitive hole lies between a bottom metallization feature and a top metallization feature. The apparatus for making the air capacitive hole includes means for plasma etching a bottom metallization layer to form the bottom metallization feature that is not in electrical contact with a substrate. Means for forming a dielectric layer over the bottom metallization feature. The dielectric layer having a tungsten plug that is in contact with the bottom metallization feature. Means for plasma etchin
Bothra Subhas
Sur, Jr. Harlan Lee
Chen Kin-Chan
Koninklijke Philips Electronics , N.V.
Zawilski Peter
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