Microelectronic integrated sensor and method for manufacturing the same

p0001The invention relates to a microelectronic integrated sensor in which a cantilever is formed. Furthermore, the invention relates to a method for manufacturing the sensor.

p0002Such sensors are used for example for measuring accelerations. The cantilever serves together with another surface as capacitance, capacitance changes are evaluated as a measurement variable. Typically, the known cantilever via a spring throughout the manufacturing process are firmly anchored in the sensor. However, the process sequences in the manufacture of the sensor lead to stress, particularly mechanical stress in the cantilever. In an incomplete relaxation of the springs, the cantilever may bend thereby. Furthermore, the forces absorbed in the springs can lead to a malfunction of the cantilever during operation.

p0003The invention has for its object to provide a sensor of the type mentioned, which is resistant to mechanical stress, especially during the manufacturing process, and thereby operates a total of particularly reliable. In addition, a method for manufacturing the sensor of the invention is to be created.

p0004The solution of this problem occurs with the characterizing features of claim 1 the method, carried out the solution with the features of claim 6. Advantageous developments are described in the dependent claims.

p0005According to an essential idea of ​​the invention, the cantilever is placed on a support, side and upper limits of travel are present, which are spaced in such a way from one edge of the cantilever, that on one hand sufficient compensating movements of the cantilever in order to avoid mechanical stress are possible, and that on the other hand movements to balance only in the region of the support are possible.

p0006In this way a complete and free relaxierbarer cantilever is created, which is on the support, for example, bearing points, placed on which it is free to move substantially and is limited laterally and from above so far in his motion that a shifting or slipping is prevented via the bearing supporting points beyond.

p0007The support and the movement restriction may conveniently be formed as a unit, preferably a blind hole-shaped surrounding the cantilever outer edge receptacle is provided. Similarly, one can also speak of a slit-shaped or slot-like receptacle of the cantilever here. The movement restrictions and the support or more specifically, the support points are preferably provided in the entire peripheral region of the cantilever. Likewise, however, both or only the bearing points or only the motion limits may be arranged point-like at some points of the cantilever.

p0008In a preferred embodiment, the movement restriction is formed in the form of a support which is guided through a recess formed in the cantilever. The movement limiting thus does not attack in this case at the outer edge of the cantilever, but in the formed recess in the edge of the cantilever.

p0009In the method for producing a micro-electronic, integrated sensor with a formed in a cavity of a cantilever, a first oxide is according to any essential idea of ​​the invention on a substrate is generated which serves as the basis for the generation of the bearing points, deposited thereon, a second oxide layer, the a has higher etch rate than the first oxide layer, a first polysilicon layer is deposited to Cantileverbildung, doped and recrystallized, in the first polysilicon layer, a hole array structure which serves for the passage of the performed at the end of the process sequence oxide etching, depositing a third oxide layer having a second oxide layer similar etching rate wherein the second and serve the third oxide layer as a base for the generation of a lateral movement-limiting, a further material layer having an etch rate applied, which is lower than the etching rate of the second and third oxide layers, depositing a second polysilicon layer to form a cover, the second in the polysilicon layer, a hole array structured and carried out by this array of holes isotropic etching of the last applied material layer, and the third, second and first oxide layer to form the cavity.

p0010With this method, a cantilever is formed in a cavity within a sensor, the lateral movement limitations formed on a formed of a first oxide layer supporting point, of from the second and the third oxide layer and an upper movement limitation formed from the upper layer of material is held movably in a predetermined range ,

p0011In the process, the first oxide is formed by a LOCOS technique, so as thermal oxide preferred. The second and third oxide layer advantageously consist of a deposited oxide, which can be formed of TEOS, for example. The fact applied material layer is in a preferred embodiment of borophosphosilicate (BPSG).

p0012During the oxide etching to form the cavity, there is the possibility that the cantilever is formed from the first polysilicon layer or a silicon layer, sucks at the support or other surface in cooperation with the etching liquid. For this reason it is advantageous to provide during the manufacturing process resist pillars that can be easily formed by a two-stage generation of the holes arrays in the second polysilicon layer. Here are structured with a first photographic technique some holes in which then resist pillars are formed. In these holes an anisotropic etch is performed first with a partially isotropic component. To generate the remaining holes of the hole array in the second polysilicon layer a resist mask is applied again, which can only be generated holes are now free and is therefore also applied in the region of the holes produced first. Here, the previously etched cavities fill with paint and engage below due to the isotropic component of the first etching and the first polysilicon layer. For the formation of this resist pillars, it is necessary that the holes used for this purpose in the array of holes of the first polysilicon layer substantially coincide with the holes of the second polysilicon layer.

p0013In the following the invention with reference to an embodiment shown in the drawing will be further explained. In detail, the schematic representations in:<dl id="dl0001"><dt>figure 1</dt><dd>a schematic cross section of a microelectronic sensor with cantilever during the manufacturing process;</dd><dt>figure 2</dt><dd>a microelectronic sensor with cantilever towards the end of the manufacturing process; and</dd><dt>figure 3</dt><dd>a partially-sectioned plan view of a microelectronic sensor.</dd></dl>

p0014In Figure 1, applied and structured in the various steps of material layers are shown. In this case, a thermal oxide is starting from a substrate 1 having a LOCOS technique produced. This is structured with a first photographic technique. It (Tetraäthyloxysilikat) is deposited an oxide to form a second oxide layer 3 by depositing a TEOS layer. This is patterned with a second photographic technique. It should be noted that this second oxide layer of deposited oxide a higher etching rate than the underlying first oxide layer 2 of thermal oxide. Then, a first polysilicon layer 4 is deposited, which is used to Cantileverbildung. This polysilicon layer 4 is then doped and recrystallized using a high-temperature treatment, thereby conducted a dopant activation. By means of a third photographic technique, this polysilicon layer 4 is structured, wherein, first, just as in the other layers also to define and structure the outer dimensions takes place, and on the other in the polysilicon layer, an array of holes 5 is produced. The holes thus generated are used later for passage of etchant for oxide etch into the underlying polysilicon layer 4 oxide layers 2 and 3. In the next step, in turn, a TEOS coating is applied to the oxide deposition. This third oxide layer 6 is patterned with a fourth photo technique for determining its external dimensions. The oxide also fills the holes voher generated in the first polysilicon layer 5th The second oxide layer 3 and the third oxide layer 6 made of the same material and thus have both the same etch rate, which is higher than that of the first oxide layer 1. In the next step, a material layer 7 is applied, which has a lower etching rate than the second and third oxide layer. But here borophosphosilicate is used. Then, a compression step is carried out and at the same time achieved a planarization effect. On the BPSG layer 7, a second polysilicon layer 8 is applied, which serves to cover the sensor. This polysilicon layer is doped 8, also recrystallized with a high-temperature process and the available dopants activated. In the following photo technique for patterning the polysilicon layer 8 on the one hand, the external dimensions of the sensor are determined and already produced for other some holes of the holes arrays 9, in which resist pillars are to be arranged. The polysilicon is etched to the shared through the mask bodies which comply substantially with holes in the underlying first polysilicon layer. 4 With a dry, anisotropic oxide etch having an isotropic component a down reaching down to the substrate 1 hole is generated in the sensor, which is substantially perpendicular and the polysilicon layers 4 and 8 engages under the area of ​​the etching hole. With a second photographic technique, the remaining holes of the holes arrays 9 are generated in the second polysilicon layer. 8 For this, a corresponding resist mask is initially applied, which also covers the holes produced by the preceding phototechnology the second polysilicon layer. 8 The holes created in the preceding etching step are filled with paint, so that resist pillars 11 forming inside the sensor. Through the remaining open holes in the second polysilicon layer 8 a wet isotropic oxide etch is then performed, which generates a cavity 10 due to the different etching rates of the oxide layers 2, 3 and 6 and the overlying BPSG layer 7, which is shown in Figure 2 , By paint prop 11 which forms the cantilever first polysilicon layer 4 is maintained above the thermal oxide 2 the support forming and prevents hard eyes during the etching process.

p0015The lacquer support 11 is removed. This method is illustrated in FIG. 2 In the next steps, the array of holes is closed again in the second polysilicon layer, as well as parts of the BPSG layer. 7 In the area of ​​the arrow 12 is a photographic technique structured a contact hole, and then carried out the contact hole. Through this contact hole metallization for contacting the cantilever is performed. With this method, therefore, a sensor has been provided whose cantilever 13 rests on a support point 14 and is carried by this. A lateral shift of the cantilever 13 is lateral movement limits 15, which must be arranged on several sides of the cantilever 13, prevented. In addition, upper limits of travel 16 are provided to prevent jamming. The sensor can now work as intended by the changing capacitances between the cantilever and the polysilicon layer 8 on the one hand and the cantilever and the substrate 1 on the other. Since the support point 14 and the lateral movement limitations of oxide 15 and the upper limit of movement 16 is composed of BPSG, the cantilever is electrically isolated from the substrate 1 and the second polysilicon layer stored eighth

p0016In figure 3 a top view is shown on the sensor, wherein the outer dashed line indicates the outer dimensions of which are determined by the second polysilicon layer. 8 This acts as a cover and is located above the underlying cantilever. The solid line shows the dimensions of the first polysilicon layer 4 in whose central region the array of holes 5 is formed. That's what also the array of holes 9 of the second polysilicon layer 8. The contact points and the moving boundaries are located in the bottom right corner arranged extension of the cantilever, but can also be placed directly on the edge is.

p0017In some applications, the top cover is not necessary, so that in these cases the cantilever directly accessible from the outside and only one type of plate is over a cavity. Such embodiments can be used for example as a pressure sensor.