JP3269173B2 - Manufacturing method of floating structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a floating structure by forming a trench on a silicon substrate and then performing anisotropic etching on the trench.

[0002]

2. Description of the Related Art Conventionally, there has been known a semiconductor acceleration sensor which detects an acceleration by detecting a resistance change due to a piezoresistance effect. In this type of semiconductor acceleration sensor, an anisotropic etching is used to produce a floating structure having an inverted triangular structure whose cross-sectional shape is surrounded by one {100} plane and two {111} planes of silicon. Thus, there is a sensor in which the accuracy and sensitivity of the sensor are improved (see JP-A-3-23676).

[0003]

However, in the conventional anisotropic etching technique as described above, if a single-side process of polishing only one side of a silicon wafer is used, only a sensor having a simple structure can be manufactured. Can not. Therefore, when manufacturing a general semiconductor acceleration sensor or the like, it must be combined with a double-side process of polishing from both sides of a silicon wafer.
The number of process steps increases and costs increase. Further, in the case of the double side process, it is necessary to attach the cover to the lower portion later, and there is a problem that the number of process steps is increased and the cost is increased. An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method capable of manufacturing a complicated floating structure by anisotropic etching even when a single-side process is used.

[0004]

According to a first aspect of the present invention, a floating structure is manufactured by forming a trench on a silicon substrate and then performing anisotropic etching on the trench. A method of using an anisotropic etching mask pattern, wherein
This is a method for manufacturing a floating structure using a correction pattern in which a rectangular trench is formed from a concave corner formed by the trench to substantially half or more of the pattern width at an angle of about 45 degrees with respect to the 0 ° direction. The invention according to claim 2 is a method of manufacturing a floating structure by forming a trench on a silicon substrate and then performing anisotropic etching on the trench portion, wherein a mirror index is used as a mask pattern for the anisotropic etching. A cross-shaped trench is formed in parallel with the {110} direction of the display, and the pattern width is approximately four minutes from the concave corner formed by the trench at an angle of approximately 45 degrees with respect to the {110} direction of the Miller index. This is a method of manufacturing a floating structure using a correction pattern in which a rectangular trench is formed up to at least one. According to a third aspect of the present invention, in the method for manufacturing a floating structure according to the first or second aspect, the floating width of the formed floating structure is varied by performing anisotropic etching while changing the pattern width stepwise. This is a method for manufacturing a floating structure provided with the following.

[0005]

According to the first and second methods, after a trench is formed on a silicon substrate, the trench is anisotropically etched using a correction mask pattern to produce a floating structure. Using this floating structure,
Acceleration and angular acceleration can be detected. According to the method of the third aspect, by providing a step in the floating state of the floating structure, it is possible to make a difference in the amount of deflection in each part of the floating structure. By detecting a signal in each part of the floating structure and performing arithmetic processing on the signal, acceleration and angular acceleration can be detected.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows a semiconductor acceleration sensor having a general floating structure which is a premise of the present embodiment. This acceleration sensor is a floating structure 1
, A beam 2, a frame 3, and a piezoresistor 4 provided on the beam 2. The floating structure 1 is a beam 2
The other end of the beam 2 is connected to the frame 3. The floating structure 1 is bent in response to the force applied to the floating structure 1 by the acceleration, and the beam 2 is distorted by the displacement of the floating structure 1. The acceleration is detected by detecting a resistance change of the piezoresistor 4 due to the distortion.

In the anisotropic etching of silicon,
The fact that the etching rate greatly differs depending on the crystal plane is used. The etching rates are (110) plane, (100) plane, and (111) plane expressed by Miller index in the descending order. FIG. 2 shows a case in which a mask material 12 is provided with a square etching pattern 11 having a side in the {110} direction of Miller index, and anisotropic etching is performed using the mask material 12. In the vicinity of the center of the square of the etching pattern 11, the surface is cut by the (001) plane.
A (111) plane with a low etching rate appears. As a result, as shown in FIG.
1) The (111) plane has an inclination angle of 54.7 ° with the plane.

[0008] On the other hand, FIG.
A case in which a mask material 14 is provided with a square etching pattern 13 having sides in a direction at an angle of 45 ° with respect to the 0 ° direction and anisotropic etching is performed using the mask material 14 is shown. In the vicinity of the center of the square of the etching pattern 13, the surface is shaved on the (001) plane. On the other hand, when the area near the side of the square is shaved by anisotropic etching, the side surface of the shaved trace becomes as shown in FIG. , (001) plane perpendicular to the (001) plane.

Next, a method of manufacturing a floating structure will be described with reference to FIG. As shown in FIG. 4A, a mask material 24 such as Si ₃ N ₄ is placed on the silicon single crystal 23, and a trench 25 is formed by reactive ion etching (RIE). As shown, a floating structure 26 is produced by anisotropically etching the trench 25. In FIG. 4A, the trench 2
Since the bottom surface and the side surface of 5 have different areas, when the bottom surface becomes a shape of only the (111) plane by anisotropic etching, the side surface has a side surface portion 27 as shown in FIG. After that, when the anisotropic etching proceeds, as described above, since the etching rate of the (111) plane is low, it is hardly removed, and only the side surface portion 27 is removed. , And the side surface is shaped like a broken line in the figure.

However, according to the above-mentioned method, the concave corner, which is the corner of silicon, formed by the trench on the silicon substrate cannot have a floating structure. The reason will be described with reference to FIG. After forming the trench, if you want to create a floating structure by anisotropic etching,
In the cross section taken along the line CC, the blank portion 32 can be formed by being cut in the oblique direction in FIG.
In the cross section taken along line -D, as shown in FIG. 5 (c), it is not possible to cut and to form the blank portion 32. Therefore, depending on the anisotropic etching, the shaded portion shown in FIG. 31 cannot be cut. Therefore, a floating structure cannot be produced at a concave corner by the above method.

Therefore, in the present invention, a floating structure is manufactured by correcting the conventional mask pattern and performing anisotropic etching using the corrected mask pattern. FIG. 6A shows an example of pattern correction at a concave corner. In the concave corner, the mask material 42 having the etching pattern 41 is provided as a correction pattern at an angle of approximately 45 degrees with respect to the {110} direction of Miller index.
A rectangular trench 43 is formed from the concave corner to approximately half or more of the pattern width W1. The floating structure is formed by performing anisotropic etching using the corrected pattern.

By the way, as shown in FIG.
When silicon A having an angle of 45 degrees with respect to the 0 ° direction is anisotropically etched, the (010) plane becomes
From the state of the shape B in FIG. 7B, it is cut until it reaches the (111) plane, and finally, it is cut into the shape C as shown in FIG. 7C. By utilizing this, anisotropic etching is performed using a correction pattern as shown in FIG. 6A, thereby making it possible to cut a concave corner in a shape as shown in FIG. 6B. . As described above, by applying a correction to the mask pattern, the above-described hatched portion in FIG. 5A can be removed, and a floating structure can be manufactured even at a concave corner.

FIG. 8 shows a modification of the above embodiment, and shows an example of a correction pattern at a portion where the mask members 52 intersect. In this correction pattern, a cross-shaped trench 54 is formed at the intersection of the crosses in parallel with the {110} direction indicated by the Miller index. In addition, in this correction pattern, a rectangular trench 53 is formed at an angle of approximately 45 degrees with respect to the {110} direction of the Miller index from the concave corner to approximately one fourth or more of the pattern width W2. I have. By performing anisotropic etching using the correction pattern and the pattern shown in FIG. 1 in combination, floating structures having various shapes can be formed.

FIG. 9 shows a capacitance detection method using a V-shaped groove 63 generated when the floating structure 60 is formed by anisotropic etching. The floating structure 60 is provided with a movable electrode 61a and a movable electrode 62a, and a fixed electrode 6 is provided on the V groove 63 at a position facing the movable electrode 61a.
1b is located at a position facing the movable electrode 62a.
2b is provided. The hatched portions in the figure indicate doping layers, and the movable electrodes 61a and 62a and the fixed electrodes 61b and 62b are N + or P + layers. The movable electrode 61a and the fixed electrode 61b constitute a capacitor, and the movable electrode 62a and the fixed electrode 62b constitute a capacitor. Since the value of the capacitance of the capacitor varies depending on the distance between the electrodes, the acceleration is detected by detecting the capacitance.

By arranging two or more components having the structure shown in FIG. 9 vertically in the sensor, a so-called multi-axis detection mechanism capable of detecting the capacitance in a plurality of orthogonal axes is provided. Semiconductor sensor or dynamic quantity sensor having Further, when the capacitance is detected by the movable electrode 61a and the fixed electrode 61b, and the detected value is fed back to the movable electrode 62a and the fixed electrode 62b, the semiconductor sensor has a servo mechanism. An optical scanner using the above-described capacitance detection method is also conceivable. This optical scanner is composed of a drive mechanism that forms an electrode in a V-groove generated when an anisotropic etching is performed to form a floating structure, and moves the floating structure by electrostatic attraction between the V-groove and the floating structure. You. Further, a light emitting source may be added to the optical scanner.

FIG. 10 shows an example in which a step is provided in the floating state of the floating structure. By setting the pattern width of the portions 71, 72, and 73 so that the portion 71 is the largest and the portion 73 is the smallest, a floating structure having steps as shown in FIG. In this case, the portion 71 is the most flexible and the portion 73 is the least flexible. By providing a step in the floating structure as described above, the range of the amount of deflection is different in each part. Therefore, by calculating the signal detected from each part, the change in electric quantity (drift) caused by the temperature can be reduced. The acceleration can be detected by canceling out. For example, when the piezoresistors are attached to the portions 71, 72, and 73, the amount of electricity generated by temperature is the same in each portion, but the amount of electricity generated by acceleration is different in each portion. For this reason, if the difference between the signal amounts detected by the respective units is obtained, the influence of the temperature is canceled out, and the acceleration can be correctly detected.

FIG. 11 shows an example of application to a piezo-type acceleration sensor. The weight 81 as a floating structure is supported by a beam 82, and the beam 82 is connected to a frame 83. When acceleration is applied to the weight 81, the beam 82 is distorted by the displacement of the weight 81, and the beam 82 is provided with a piezoresistor 84 to detect the distortion. By detecting a change in resistance of the piezo resistor 84, acceleration is detected.

FIG. 12 shows an example of application to a piezo-type angular acceleration sensor. This sensor can rotate around a fixed shaft 91, and four piezoresistors 94 are radially provided on four sides of the fixed shaft 91. E- in the figure
Taking the cross section along the line E, as shown in FIG.
The two flat surfaces of the upper side 95 that rotates when the second member 2 is applied and the lower side 96 that is connected to and fixed to the substrate 98 are fixed shafts 9.
Except for the part 1, the parts are provided facing each other with a gap 97 therebetween. In FIG. 12, only the upper side 95 is shown for simplification. When a moment 92 is applied to this sensor and the upper side 95 rotates about the fixed shaft 91, the angular acceleration is detected by detecting a resistance change of the piezo resistor 94. The means for detecting the acceleration and the angular acceleration is not limited to the above-described piezoresistor but may be variously modified. For example, a piezoelectric element may be used.
In addition, if the above-described floating structure is used for a sensor for detecting acceleration or the like, a floating structure having a large mass can be manufactured, so that sensor sensitivity is improved.

[0019]

As described above, according to the first and second aspects of the present invention, a floating structure is manufactured using a correction pattern as a mask pattern when anisotropically etching a trench portion. Even a floating structure having a complicated shape can be manufactured by the process. If the floating structure manufactured in this way is used for a sensor for acceleration detection or the like, a floating structure having a large mass can be manufactured, so that the sensor sensitivity is improved. Also,
According to the present invention, since the gap between the substrate and the floating structure can be widened, unlike the conventional case, the gap is narrow and a large viscous force is not applied. Further, since the single-side process is used, the number of manufacturing steps can be reduced and the manufacturing can be performed at low cost. According to the third aspect of the present invention, a floating structure having a step in a floating state can be obtained. In addition to the above-described effects, a signal detected in each part of the floating structure is arithmetically processed.
It is possible to detect the amount of electricity generated only by acceleration or angular acceleration.

[Brief description of the drawings]

FIG. 1 is a perspective view of a semiconductor acceleration sensor having a general floating structure.

FIGS. 2A and 2B are views for explaining how to remove silicon according to the crystal orientation of silicon by anisotropic etching, wherein FIG. 2A is a plan view and FIG. 2B is a cross-sectional view taken along line AA.

FIGS. 3A and 3B are views for explaining how to remove silicon according to the crystal orientation of silicon by anisotropic etching, wherein FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along line BB.

4A and 4B are diagrams for explaining a method of manufacturing a floating structure, wherein FIG. 4A is an end view of the semiconductor sensor when a trench is formed, and FIG. 4B is an end view of the semiconductor sensor when a floating structure is manufactured. is there.

5A and 5B are diagrams for explaining that a concave corner cannot be formed in a floating structure, where FIG. 5A is a plan view and FIG.
FIG. 4C is a sectional view taken along line D-D.

FIG. 6A is a plan view of a correction pattern at a concave corner according to an embodiment of the present invention, and FIG. 6B is a view showing how to cut after anisotropic etching.

FIGS. 7A, 7B, and 7C are diagrams for explaining how to cut by anisotropic etching.

FIG. 8 is a plan view of a correction pattern at an intersecting portion.

FIG. 9 is a cross-sectional view of a capacitance type semiconductor sensor using a V-groove.

FIG. 10 is a cross-sectional view of a semiconductor sensor including a floating structure having a step.

FIG. 11 is a perspective view of a piezo-type acceleration sensor.

FIG. 12 is a perspective view of a piezo-type angular acceleration sensor.

FIG. 13 is a sectional view taken along line EE of the angular acceleration sensor.

[Explanation of symbols]

 1, 26, 60, 81 Floating structure 4, 84, 94 Piezoresistor 11, 13, 41 Etching pattern 12, 14, 24, 42, 52 Mask material 25, 43, 53, 54 Trench 61a, 62a Movable electrode 61b, 62b fixed electrode

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 29/84 G01L 9/04 101

Claims (3)

(57) [Claims] 1. A method of manufacturing a floating structure by forming a trench on a silicon substrate and then performing anisotropic etching on the trench, wherein a mirror pattern represented by a Miller index is used as a mask pattern for the anisotropic etching. A method of manufacturing a floating structure, comprising using a correction pattern in which a rectangular trench is formed from a concave corner formed by a trench to substantially half or more of a pattern width at an angle of about 45 degrees with respect to a {110} direction. Method. 2. A method of manufacturing a floating structure by forming a trench on a silicon substrate and then performing anisotropic etching on the trench, wherein a mirror pattern represented by a Miller index is used as a mask pattern for the anisotropic etching. A cross-shaped trench is formed parallel to the {110} direction, and a pattern width of about 4 from the concave corner formed by the trench at an angle of about 45 degrees with respect to the {110} direction indicated by Miller index.
A method of manufacturing a floating structure, comprising using a correction pattern in which a rectangular trench is formed to at least one-half. 3. The method for manufacturing a floating structure according to claim 1, wherein a step is provided in a floating state of the formed floating structure by performing anisotropic etching while changing a pattern width stepwise. A method for producing a floating structure.