Abstract:
A housing for a semiconductor sensor configuration, in which a sensor and an evaluation logic are integrated in a semiconductor body is disclosed. The housing has a base body upon which the semiconductor body is applied and a cover that encloses the semiconductor body in the base body. The cover is directly set on the base body of the housing and contains a membrane and/or labyrinth.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of copending International Application PCT/DE97/02845, filed Dec. 5, 1997, which designated the United States. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention concerns a semiconductor sensor component with a semiconductor body in which both a sensor and an evaluation circuit are formed in an integrated manner and are protected by an encapsulation. 
     It is known that semiconductor sensors must be protected against the effects of process and environment. At the same time, it is necessary that the semiconductor sensor remains accessible for the medium to be measured. For example, the configuration for the semiconductor pressure sensor must allow the actual semiconductor pressure sensor to be coupled to the pressure to be measured. In other words, a changing pressure must be able to exert an effect on the surface of the semiconductor sensor. The same applies, for example, for temperature sensors, humidity sensors, etc. In this connection care must be taken that the protective case of the semiconductor sensor introduces the minimum possible delay in performing the measurement. 
     In an existing semiconductor pressure sensor configuration the semiconductor body of the actual semiconductor sensor is accommodated on a circuit board in an inner case equipped with a membrane, which case is provided together with an evaluation logic circuit in an outer case. Access of the measuring medium, i.e. mostly air or gas, to the inner case proceeds over a silicone membrane of the outer case. A construction of this kind leads inevitably to relatively large modules since the semiconductor sensor and the evaluation logic circuit are provided in different semiconductor bodies. 
     Semiconductor sensor configurations in which the actual semiconductor sensor and the evaluation logic circuit are combined in a single semiconductor body must be accommodated in a case that is open on one side. Up to now, after a semiconductor body of this kind has been bonded in the case open on one side, the semiconductor body is covered with silicone gel or a similar material and embedded. It has been found, however, that this kind of covering material does not provide adequate mechanical protection for the semiconductor body and that, also, its surface is adhesive to a certain extent that is a hindrance in practical applications. Further disadvantages are the danger that mechanical influences might destroy the semiconductor body and the effect of particles that settle on the surface of the semiconductor sensor configuration and can influence the characteristic curve of the sensor. 
     U.S. Pat. No. 4,732,042, for example, describes a semiconductor pressure sensor configuration in which the semiconductor is embedded in silicone rubber inside a case which is provided with a membrane on one side. In this semiconductor sensor configuration the underside of the semiconductor body is freely accessible through a hole in the case so that here there exists the danger of mechanical damage. This semiconductor sensor configuration also has no evaluation electronics integrated in the semiconductor body. 
     Published, European Patent Application EP 0 286 867 A describes a semiconductor pressure sensor configuration in which the semiconductor body is fixed to a ribbon cable and covered with a soft plastic synthetic material. The soft plastic synthetic material is placed inside a case with an opening so that the pressure is transferred to the semiconductor body over the soft plastic synthetic material. Here too, it is possible for the semiconductor body to incur damage because the soft plastic synthetic material does not always offer reliable protection against strong mechanical effects. 
     The technique is also known from Published, Non-Prosecuted German Patent Application DE 44 36 485 A, of accommodating silicon strain gages inside a case in a gel-based medium in a device for determining acceleration. The gel-based medium is relatively soft so that there is no certain guarantee that the silicon strain gages are protected against mechanical effects. 
     From “Habekotte E. et al., in: Elektronik 1/5.1.1990, p. 80-87” and “Kayal H. A., Rauch N. in: Elektronik 9/29.4.1988, p. 112-117” semiconductor sensor devices are known in which the sensor and the evaluation logic circuit are integrated together in the semiconductor body. As a result both manufacturing costs and the dimensions of the component are reduced. 
     From Published, Non-Prosecuted German Patent Application DE 41 33 061 an earlier type of pressure sensor is known in which a porous plate in the outer case is located around a measuring element. The outer case protects the measuring element from direct contact with liquids. The porous plate consists of PTFE and although it prevents the passage of liquid, it allows gases through which can attack the measuring element. 
     U.S. Pat. No. 5,436,491 shows another pressure sensor with an outer case. The case consists of steel or a similar material. It has an upwards facing open area which is closed with a diaphragm of metal. The semiconductor pressure unit is located inside the case on a base made of glass or a similar material. 
     A pressure sensor with a case consisting of a lower and an upper partial case is described in U.S. Pat. No. 4,914,954. The pressure sensor is located inside the combined case; the case is closed by a labyrinth. 
     Finally, a pressure sensor in an open case is known from Published, Non-Prosecuted German Patent Application DE 44 13 274 A. By using a membrane the case is covered extensively and closed. This configuration also does not always provide reliable protection of the pressure sensor against strong mechanical effects. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a semiconductor sensor component which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, in which the semiconductor body is accessible for the medium to be measured but is at the same time reliably protected against damage even in the presence of strong mechanical effects. 
     With the foregoing and other objects in view there is provided, in accordance with the invention, a semiconductor sensor component, including: 
     a semiconductor body having both a sensor and an evaluation logic circuit formed in an integrated manner; 
     an encapsulating component formed by a molding process of an electrically insulating material enclosing at least partially the semiconductor body and providing the semiconductor body with mechanical protection, the encapsulating component, containing: 
     a main case body having edges for housing the semiconductor body; 
     a lid having a main lid body with edges and a through opening formed therein, the lid setting directly on the main case body such that the edges of the main lid body lying against the edges of the main case body; and 
     a protective device disposed on the main lid body of the lid for closing the lid, the protective device being permeable to a medium to be sensed via the through opening, the protective device acting as a shield against 
     mechanical stresses and having at least one of a membrane interrupting the through opening and a labyrinth having several winding passages leading to the through opening. 
     Thus in the invention the sensor and the evaluation electronics are integrated in one semiconductor body. The semiconductor body is not, however, provided in an inner case and additionally in an outer case. Instead, only one case is used whose lid with the membrane and/or the labyrinth is so configured that it is also able to withstand greater mechanical stresses. 
     For this purpose the lid can have as the membrane, for example, a metal foil which has through-openings in a lid main body made of a synthetic material and is thus exposed only in these through openings. Thus the metal foil here is not exposed over its entire area but, preferably, is for the most part extrusion-coated with the synthetic material so that in the case of a pressure sensor the pressure is transmitted only over the through openings onto the metal film acting as a membrane. 
     It is also possible to support the membrane at an edge of the lid main body formed of the synthetic material and having an opening, on its underside. In this way the membrane is protected over its entire area and is accessible solely via the opening in the lid main body. 
     The membrane can also be fixed to a ring-shaped projection within the edge of the lid main body with an opening. In this way it is possible to support the membrane “all-round” which as a result of its resulting advantageous intrinsic oscillation improves the response behavior of the semiconductor sensor configuration. 
     It is useful to provide the opening in the middle of the lid main body so that the medium to be measured is also applied to the middle of the membrane. 
     Instead of the membrane it is also possible to provide a labyrinth at the inner surface of the lid main body. If applicable a membrane and a labyrinth can also be used together. 
     The labyrinth can, for example, contain a spiral groove which leads from an outer opening located at the edge of the lid main body to an inner opening located in the middle of the lid main body and which is covered with a metal foil on the inside surface of the lid main body. With such a configuration the semiconductor body is protected extremely reliably against mechanical effects because there is no direct, straight-line access between the outer and the inner openings. 
     Advantageously it is possible to place a sealing medium, for example in the form of a drop of liquid, inside the labyrinth. A drop of oil can be used as the drop of liquid. In response to pressure changes the drop of liquid moves freely to and fro inside the meander-like labyrinth and thereby reliably seals the labyrinth between the outer and inner openings. 
     The labyrinth can also be formed through a spiral-shaped web which is embedded between the lid main body and a foil and which runs between an outer opening located at the edge of the lid main body and an inner opening located in the middle of the foil. A web of this sort can be fabricated in a simple way by an injection molding tool. 
     The cover can also consist of an injection molded part in which at least one through opening is provided such that a straight-line path into the inside of the case is prevented, i.e. such that this through opening also forms a “labyrinth”. 
     Furthermore, it is possible to fabricate the lid from two synthetic material parts fitting into each other which are coupled together through a spring medium and which expose a through opening. This prevents straight-line access to the inside of the case, as soon as a certain pressure is applied to the spring medium. Here too the through opening is a “labyrinth” which prevents mechanical damage to the semiconductor body. 
     The semiconductor-sensor configuration according to the invention is simple to fabricate. The main bodies of the case and lid can be led on separate assembly lines to a work station and be combined there with each other. Also, the lid main body and, for example, a metal foil can be conveyed on separate assembly lines and combined together at the work station to form the lid. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a semiconductor sensor component, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic, sectional view through a case for a semiconductor sensor configuration according to the invention; 
     FIG. 2 is a sectional view through a lid according to a first exemplary embodiment; 
     FIG. 3 is a sectional view through the lid according to a second exemplary embodiment; 
     FIG. 4 is a sectional view of the lid according to a third exemplary embodiment; 
     FIG. 5 is a perspective, partially cut-away view of the lid according to the third exemplary embodiment; 
     FIG. 6 is a sectional view through the lid according to a fourth exemplary embodiment; 
     FIG. 7 is a sectional view of detail A of the lid shown in FIG. 6; 
     FIG. 8 is a perspective, bottom view of the lid shown in FIG.  6 ; 
     FIG. 9 is a sectional view through the case according to a fifth exemplary embodiment; 
     FIG. 10 is a fragmented, perspective view for explaining a fabrication process of the case; 
     FIG. 11 is a sectional view through the case according to a sixth exemplary embodiment; 
     FIG. 12 is a top plan view of the lid according to a seventh exemplary embodiment; 
     FIGS. 13 and 14 are sectional views through the lid of FIG. 12; 
     FIGS. 15 and 16 are sectional views through the lid according to an eighth exemplary embodiment; and 
     FIG. 17 is a perspective view of the lid according to the eighth exemplary embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In all the figures of the drawing, sub-features and integral parts that correspond to one another bear the same reference symbol in each case. Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a case according to the invention for a semiconductor sensor configuration. The case consists of a case main body  1 , a semiconductor body  2  attached thereto, and a lid  3  which closes the semiconductor body  2  inside the case main body  1 . The semiconductor body  2  is bonded over connecting wires that are shown purely schematically in FIG.  1 . An inside of the case must be accessible for a medium to be measured whereby, for example, the lid  3  can contain a membrane  5  that is exposed via a through opening  6  in order that in the case of a pressure sensor a pressure can exert an effect on the semiconductor body  2  via the membrane  5 . 
     FIG. 2 now shows a first concrete exemplary embodiment of the invention. Here the lid  3  contains a lid main body  4  formed of a synthetic material in which a metal foil of the membrane  5  is embedded which is injection molded into the synthetic material of the lid main body  4 . Several of the through openings  6  are provided in the main lid body  4  so that the membrane  5  is exposed in the through openings  6  and can transmit the pressure into the inside of the case. 
     The lid shown in FIG. 2 is, for example, laid at its edge  7  on an edge  8  of the case main body  1  and glued together with this after the semiconductor body  2  has been bonded in a suitable way. 
     FIG. 3 shows a second embodiment of the invention in which a film  5 ′ of a synthetic material such as silicone, or a metal foil  5 ′ is fixed to the raised edge  7  of the lid main body  4 . The main lid body  4  formed of the synthetic material has here in its middle the through opening  6  so that the effect of a pressure exerted from the outside is applied to the membrane  5 ′ at its middle, which favorably influences its response behavior. 
     FIG. 4 shows in a third exemplary embodiment of the invention a variant of the exemplary embodiment of FIG.  3 . Here the membrane  5 ′ is suspended at a circular prominence  28  on the underside of the lid main body  4  so that a square or rectangular suspension according to the exemplary embodiment of the invention of FIG. 3 can be modified into a round suspension, which is favorable for the response behavior of the membrane  5 ′. 
     FIG. 5 shows the lid of FIG. 4 in perspective, whereby the round shape of the membrane  5 ′ can be clearly recognized. The through opening  6  is shown in FIG. 5 for reasons of clarity, although it is actually covered by the membrane  5 ′. 
     In the exemplary embodiments of FIGS. 3 to  5  the membrane  5 ′ is configured to be corrugated, which has proved useful for the transmission of pressure. 
     FIG. 6 shows a fourth exemplary embodiment of the invention in which a spiral-shaped labyrinth  9  has been worked into the main lid body  4 , which labyrinth  9  leads from an outer opening  10  to an inner opening  11  as indicated schematically in FIG.  8 . FIG. 7 shows a detail of the labyrinth  9  in the main lid body  4 . 
     The labyrinth  9  can, for example, be incorporated in the main lid body  4  in that this is provided during casting with an appropriate groove and is then “sealed” with, for example, a metal foil or plastic film  12 . For reasons of clarity the foil  12  is illustrated in FIG. 6 in an “exaggerated” way. The labyrinth  9  exerts a damping effect on the transmission of the pressure since a certain amount of time passes until a pressure change affecting the outer opening  10  reaches the inner opening  11  through the labyrinth  9 . 
     As illustrated schematically in FIG. 8, a drop of a liquid  13 , for example oil, can be placed in the labyrinth  9  in order to serve as a further seal between the outer opening  10  and the inner opening  11 . 
     FIG. 9 shows a case according to a fifth exemplary embodiment of the invention in which the labyrinth  9  is provided in the main lid body  4 , similarly to the fourth exemplary embodiment of FIGS. 6 to  8 , and closed by an inner surface of the foil  12  or also of a thin copper part. The inner surface can be bonded to the main lid body  4  by an adhesive glue. At its edge  7 , the main lid body  4  is glued to the edge  8  of the main case body  1 . External electrical connections  14  are simply shown schematically in FIG.  9 . 
     In contrast to the exemplary embodiment of FIGS. 6 to  8 , the outer opening  10  in FIG. 9 is located in the middle of the main lid body  4  while the inner opening  11  is placed at the edge of the main lid body  4 . Thus it is not absolutely necessary to provide the inner opening  10  in the middle of the main lid body  4 , although this has proved to be useful in order to enable the pressure on the semiconductor body  2  to be exerted “in the middle”. 
     FIG. 10 shows schematically how the case according to the invention can be fabricated via assembly line production. On a first assembly line  15  the main lid body  4  with the labyrinth  9  is delivered and is taken up by a non-illustrated suction tester. It can be useful to place the outer opening  10  not in the middle (as shown) in order that the suction tester can reliably take up the main lid body  4 . The main lid body  4  is then glued to the foil  12  that is delivered on a second assembly line  16  and pulled from an underlay  17 . The combination of the main lid body  4  with the foil  12  is indicated schematically through a bracket with an arrow  18 . The main lid body  4  and the foil  12  glued to it are then glued by a tampon glue application to the outer edge  8  of a main case body  1 , which is delivered on a third assembly line  19 . 
     In this way the case according to the invention can be assembled simply by the use of three assembly lines. 
     FIG. 11 shows a sixth exemplary embodiment of the invention in which the main lid body  4  consists of a thin metal or synthetic material plate to which a spiral-shaped web  20  is glued which is in turn provided with the foil  12  of metal or a film  12  of synthetic material. The web  20  thereby forms the meander-shaped labyrinth  9  between the outer opening  10  and the inner opening  11 . The web  20  can be advantageously fabricated as an injection molded part. As in the above exemplary embodiment, the drop of liquid  13  can also be placed in the labyrinth  9  to provide a seal. 
     FIGS. 12 to  14  show a seventh, particularly robust exemplary embodiment for the lid  3  of the case  1  according to the invention. Here the lid  3  includes an injection molded part which can be fabricated with three cores for a total of three outer openings  10  (see FIG. 12) and one core for the inner opening  11 . As can be seen from FIGS. 13 and 14, there is no straight-line through path from the outer opening  10  to the inner opening  11  so that to this extent a labyrinth exists here as well. In this way a reliable protection of the semiconductor body  2  beneath the lid  3  is guaranteed. 
     Finally, FIGS. 15 to  17  show an eighth exemplary embodiment of the invention in which a “spring medium”  23  is provided between two lid halves  21  and  22  which engage one another by use of a nose, in which the spring medium  23  can be compressed under the influence of pressure. If pressure is exerted from the outside on the lid half  21 , the spring medium  23  is compressed (see FIG. 16) whereby a through opening  24  is exposed. The two lid halves  21  and  22  consist of a synthetic material and can be fabricated by injection molding in a similar way to the main lid body  4  of the exemplary embodiments of FIGS. 12 to  14 . Instead of the single through opening  24  shown in FIG. 17, it is possible to form, for example, three through openings. 
     The lid of the eighth exemplary embodiment makes possible a semiconductor pressure sensor that does not respond below a specific threshold value, namely until the spring medium  23  is compressed. For the spring medium  23  it is possible to use foam, a gas column or rubber. 
     The case according to the invention is, of course, not exclusively limited to use for a semiconductor sensor configuration in which the sensor and the evaluation logic circuit are integrated in one semiconductor body. It can also be used to advantage in a semiconductor sensor configuration in which the sensor and the evaluation logic circuit have different semiconductor bodies and are accommodated in a single shared case or in two separate cases. In the second variant only the sensor is provided with a case according to the invention.