Pressure sensor and manufacturing method thereof

1. A pressure sensor comprising:

a sensor chip having a first semiconductor layer that has an opening portion, and a second semiconductor layer, which has a recessed portions that forms a diaphragm, formed on the first semiconductor layer; and

a base, bonded to the sensor chip, having a pressure guiding hole that connects to the opening portions; wherein

the recessed portion of the second semiconductor layer is larger than the opening portion of the first semiconductor layer; and

the opening diameter of the opening portion of the first semiconductor layer at the second semiconductor layer side is larger than the opening diameter at the base side.

2. A pressure sensor as set forth in claim 1 , wherein an insulating layer having an opening portion is formed between the first semiconductor layer and the second semiconductor layer.

3. A pressure sensor as set forth in claim 1 , wherein a non-bonded portion, wherein a gap is provided between the sensor chip and the base, is formed at a periphery of a bonded portion between the sensor chip and the base.

4. A pressure sensor as set forth in claim 1 , wherein:

the edge of the opening in the recessed portion of the second semiconductor layer extends to the outside with a width dimension of no less than 5 μm and no more than 50 μm beyond the side wall of the opening portion on the second semiconductor layer side in the first semiconductor layer.

5. A method for manufacturing a pressure sensor that has a sensor chip that is provided with a first semiconductor layer and with a second semiconductor layer that forms a diaphragm that is a pressure sensitive region, comprising:

a step for anisotropically etching the first semiconductor layer to form an opening portion in the first semiconductor layer in a part that becomes the pressure sensitive region;

a step for forming a passivating layer on the side wall in the opening portion of the first semiconductor layer with a thickness distribution so that the film thickness will be thinner on the second semiconductor layer side;

a step, after the formation of the passivating layer, for etching the side wall in the opening portion of the first semiconductor layer so as to form an opening portion of the first semiconductor layer so that the opening diameter on the second semiconductor layer side will be larger than the opening diameter on the other side, and also for etching the second semiconductor layer in the part that will form the pressure sensitive region to form, in the second semiconductor layer, a recessed portion that is larger than the opening portion of the first semiconductor layer, in order to form the diaphragm; and

a step for bonding the base to the sensor chip.

6. A method for manufacturing a pressure sensor as set forth in claim 5 , further comprising:

a step, after the step for forming the opening portion by anisotropically etching the first semiconductor layer, for providing an opening portion by etching an insulating layer that is provided between the first semiconductor layer and the second semiconductor layer; wherein

in the process for forming the opening portion in the first semiconductor layer, the insulating layer that is provided between the first semiconductor layer and the second semiconductor layer is used as an etching stopper, and etching is performed anisotropically.

7. A pressure sensor manufacturing method as set forth in claim 5 , wherein:

in the step for bonding the base to the sensor chip, a non-bonded portion, provided with a gap between the sensor chip and the base, is formed at a periphery of a bonded portion between the sensor chip and the base.