The present invention relates to a method for manufacturing micromechanical sensors, in particular pressure difference sensors.
The present invention also relates to a micromechanical sensor.
Although the present invention may, in general, be applied to any kind of micromechanical sensor, the present invention is described with respect to micromechanical sensors in the form of pressure difference sensors.
Micromechanical pressure difference sensors usually include semiconductor resistors, which are used as mechanical-electrical transducers. These detect not only mechanical stresses resulting from the influence of pressure on a corresponding diaphragm, but also stresses from mechanical interfering influences. Mechanical stresses occur, on the one hand, during the connection of the pressure difference sensor, for example due to deformation of a circuit board on which the pressure difference sensor is situated, or also due to contacting with the aid of soldering, during which a deformation of the layer structure/package occurs, and, on the other hand, also due to stresses from the sensor itself. The latter may stem from different temperature behavior of different layers of the layer structure, for example, or also from different temperature behavior of a metallization, in particular when large-surface-area bond lands are applied. The above-described effects are additionally dependent on the manufacturing history of the pressure difference sensor, i.e., the sequence of the manufacturing steps, which may only conditionally be compensated for by an adjustment prior to delivery of the pressure difference sensor.
Proceeding from this, in accordance with the present invention, it is provided to mechanically decouple parts of the pressure difference sensor, i.e., the diaphragm and the corresponding micromechanical pressure sensors, for example, from the remaining pressure difference sensor, for example by essentially clearing the diaphragm of the pressure sensor on all sides with the aid of trenching, i.e., by essentially clearing the diaphragm on all sides with the aid of etching, with the exception of individual connections to be able to run electrical feed lines via these. The pressure sensor is exposed in the process by a full-surface-area rear side trench, and the rear side trench is subsequently sealed again in a complex process with the aid of a wafer bond with a rear side cap. An additional front side cap having pressure access holes protects the exposed pressure sensor from above.
In one specific embodiment, the present invention provides a method for manufacturing a micromechanical sensor, in particular a pressure difference sensor, including the steps:
In one further specific embodiment, the present invention provides a micromechanical sensor, manufactured using a method as recited in one of claims 1 through 10, in particular, the micromechanical sensor being designed as a pressure difference sensor, the pressure sensor diaphragm including a functional layer and a gel applied onto the functional layer.
In other words, specific embodiments of the present invention make an exposure of the functional layer on all sides possible, a partial filling with gel of the clearances, trenches and gaps resulting from the partial exposure taking place to seal the front side from the rear side.
One of the achieved advantages is that, in this way, an exposure of a functional layer on all sides, in particular, for forming a pressure sensor diaphragm, is made possible, so that the functional layer area is decoupled from stress from the package or from the application site of the package. Moreover, a filling with gel may take place at the wafer level, and thereby enable more favorable integrated circuit packaging. Another advantage is that a stress decoupling as a result of filling the clearly defined trench areas, for example gaps and the like, in the substrate may take place in a precise manner. This reduces the variance between different sensors since high adhesive thicknesses, which are difficult to control, are no longer necessary.
The term “trenching” shall be understood in the broadest sense and denotes, in particular, the creation of trenches, holes, gaps or the like by removing material from a base material, for example with the aid of etching, in particular reactive ion etching in silicon.
The term “essentially” or “approximately” shall be understood in the broadest sense and refers, in particular, to deviations, variations, tolerances and the like with respect to dimensions, positions, spacings, distances, fractions or the like. For example, the expression “a size is essentially identical to a second size” denotes that the two sizes may deviate from one another, in particular by 100%, preferably by 75%, in particular by 50%, preferably by at least 25%, in particular by 20%, preferably by 10%, in particular at least 0.5%, preferably less than 0.1%, in particular less than 0.001% or the like. For example, the expression “approximately isotropic trenching step” denotes that more than 50%, in particular more than 60%, preferably more than 70%, in particular more than 80%, preferably more than 90%, in particular more than 95% of the trenching takes place isotropically.
The term “gel” shall be understood in the broadest sense and denotes, in particular, a dispersing system which includes at least two components, in particular a polymer network and a solvent. The term “gel” denotes, in particular, a soft mass, and a gel is created when the polymer network has absorbed the entire solvent. In particular, the term “gel” covers both already cross-linked gel and not yet cross-linked gel. Examples of gels are silicone hydrogels, hydrogels based on polyacrylamide or polymacon (CAS number 25053-81-0) or hydrogels based on cross-linked polymers, e.g., poly(2-acrylamido-2-methyl-1-propanesulfonic acid), polyethylene glycol or polyvinylpyrrolidone.
Further features, advantages and further specific embodiments of the present invention are described hereafter or become apparent thereby.
According to one advantageous refinement of the present invention, multiple rear side trench holes for creating the at least one rear side trench area are generated. One of the advantages achieved thereby is that an easy creation of the at least one rear side trench area is made possible.
According to one further advantageous refinement of the present invention, at least one cavity for forming a first connecting trench area between rear side trench holes is generated. In this way, multiple rear side trench holes may be fluidically connected in a simple manner.
According to one further advantageous refinement of the present invention, multiple front side trenches for creating the at least one front side trench area are generated. In this way, on the one hand, an exposure of the functional layer on almost all sides may be achieved in a simple manner and, on the other hand, a suspension for the sensor diaphragm may be created, for example.
According to one further advantageous refinement of the present invention, a stop layer is created between the substrate and the functional layer, and the at least one rear side trench area is created up to the stop layer, and the stop layer is subsequently removed in the area of the sensor diaphragm. With the aid of a stop layer, the process variations may be reduced with a time-controlled manufacturing process.
According to one further advantageous refinement of the present invention, at least one cavity for forming at least one second connecting trench area between multiple front side trench areas is generated. In this way, a fluid connection may be established in a simple manner between two front side trench areas, so that the energy storage structure, for example in the form of a long spring, forms, on which the almost completely exposed sensor diaphragm area is mounted.
According to one further advantageous refinement of the present invention, a diameter of the rear side trench holes is selected to be smaller than the diameter of the cross section of at least one cavity of a first and/or a second connecting trench area(s). In this way, the gel flowing through the rear side of the substrate, for example to a mounting of a wafer, and soiling it, may be easily prevented; the gel may then flow, in particular, only horizontally.
According to one further advantageous refinement of the present invention, multiple first connecting trench areas are created, which are fluidically connected to one another via at least one trench channel, and at least one of the first connecting trench areas being created directly beneath the functional layer for exposing it. In this way, it is possible, on the one hand, to create communicating cavities, and, on the other hand, a soiling of the lower side of the functional layer by particles is even further reduced.
According to one further advantageous refinement of the present invention, the at least one front side trench area is created chronologically before the at least one rear side trench area. One of the advantages achieved thereby is that, initially, front side trench areas are completely created and then, from the rear side, the corresponding rear side trench areas, which overall simplifies the manufacture of a micromechanical sensor.
According to one further advantageous refinement of the present invention, the micromechanical sensor is designed as a pressure difference sensor including a functional layer designed as a pressure sensor diaphragm. In this way, a pressure difference sensor is provided in a simple and cost-effective manner.
Further main features and advantages of the present invention are derived from the figures, and from the associated description of the figures.
It shall be understood that the above-mentioned features and those still to be described hereafter may be used not only in the particular described combination, but also in other combinations, or alone, without departing from the scope of the present invention.
Preferred embodiments and specific embodiments of the present invention are shown in schematic form in the figures and are described in greater detail in the description below, identical reference numerals referring to identical or similar or functionally equivalent components or elements.
In a first step according to
In a second step according to
In a third step according to
In a fourth step according to
In a fifth step according to
In a sixth step according to
In a seventh step according to
In an eighth step according to
In a first step according to
In a second step according to
In a third step according to
In a fourth step according to
In a fifth step according to
In a sixth step according to
The first step according to
In a second step according to
In a third step according to
In a fourth step according to
In a first step according to
In a second step according to
In a third step according to
In a fourth step according to
In all specific embodiments, the structures shown as bar springs 17 may also be designed or separated as meander-shaped springs, springs having angles, or springs having arbitrary curve shapes. An arbitrary number of springs may be designed for contacting the area of the pressure sensor diaphragm. The springs may be combined with one another and/or split up in the process and are used for mounting and, if necessary, contacting sensors in the area of the pressure sensor diaphragm.
In summary, at least one specific embodiment has at least one of the following advantages or enables one of these advantages:
Although the present invention has been described based on preferred exemplary embodiments, it is not limited thereto, but is modifiable in a variety of ways.
Number | Date | Country | Kind |
---|---|---|---|
102017210691.3 | Jun 2017 | DE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2018/065775 | 6/14/2018 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2019/001974 | 1/3/2019 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5427975 | Sparks | Jun 1995 | A |
20150141854 | Eberle | May 2015 | A1 |
20160327446 | Classen | Nov 2016 | A1 |
Number | Date | Country |
---|---|---|
102004043356 | Mar 2006 | DE |
102008002579 | Dec 2009 | DE |
102010042113 | Apr 2012 | DE |
102015120881 | Jun 2017 | DE |
0624900 | Nov 1994 | EP |
H0715019 | Jan 1995 | JP |
2000171318 | Jun 2000 | JP |
2009080095 | Apr 2009 | JP |
2013154465 | Aug 2013 | JP |
WO-2015106855 | Jul 2015 | WO |
Entry |
---|
International Search Report for PCT/EP2018/065775, dated Sep. 14, 2018. |
Number | Date | Country | |
---|---|---|---|
20200209089 A1 | Jul 2020 | US |