JP2011083844A - Evaluation method for mems device, and manufacturing method for mems device - Google Patents

Abstract

A method of measuring a resonance frequency error by driving a MEMS device and evaluating a dimensional error in a manufacturing process is realized.
A method for evaluating a MEMS device includes a lower electrode formed on a surface of a substrate and a first drive having a space on the surface of the lower electrode and extending in parallel and opposite directions. It has an arm 62 and a second drive arm 64, measures the resonance frequency of each of the first drive arm 62 and the second drive arm 64, and resonates from the resonance frequency of each of the first drive arm 62 and the second drive arm 64. Calculating a median value of the frequencies, and calculating a difference between the resonance value of each of the first drive arm 62 and the second drive arm 64 and the median value. The shift amount of the arm 62 and the second drive arm 64 is evaluated.
[Selection] Figure 1

Description

  The present invention relates to a method for evaluating a MEMS device and a method for manufacturing the MEMS device.

  MEMS (Macro Electro Mechanical Systems) is one of fine structure forming technologies, and is a fine mechanical and electrical system, which is manufactured using semiconductor manufacturing technology. The MEMS structure is a fine elastic body, a rotating body, etc. It has a three-dimensional movable body.

  A process standard defined in semiconductor manufacturing is determined within a range that guarantees electrical characteristics of a circuit to be created. Therefore, it is said that there is no problem in circuit characteristics (electrical characteristics) if there is a slight deviation within the standard. However, the behavior or behavior characteristics of a MEMS device produced using semiconductor manufacturing technology greatly depends on the length of the movable body.

  As a typical MEMS device, a lower electrode is formed on a substrate surface, a space is formed on the surface of the lower electrode, a cantilevered drive arm is formed as a movable body, and the drive arm and the lower electrode are formed. A MEMS device has been proposed in which a potential difference is generated between them and the drive arm is driven by static electricity (see, for example, Patent Document 1).

US Pat. No. 7,0024,36

  Since the behavior characteristic of the MEMS device configured as in Patent Document 1 depends on the length of the driving arm and the crossing area between the driving arm and the lower electrode, the manufacturing process of the driving arm, and the other including the lower electrode If the manufacturing process of the functional element is a separate process, there may be a relative dimensional error between the drive arm and the lower electrode or other functional elements. The accuracy of these adjustments affects the behavior and behavior characteristics of the drive arm. To do.

  When such a MEMS device is used as a resonator, a desired resonance frequency may not be obtained due to a drive arm length error caused by this alignment error, and this MEMS device is used as a switch. In some cases, it may be possible not to drive at a desired voltage.

  In order to solve these problems, a method of evaluating these errors by directly measuring the length dimension of the drive arm, the formation position and dimension of the lower electrode, is employed. However, as described above, since a MEMS device is a microstructure that is manufactured using semiconductor manufacturing technology, it takes time for measurement, an error tends to occur in the measurement itself, and the accuracy of the measuring instrument itself. There is a problem that there is a limit to the dimensional accuracy that can be evaluated.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A MEMS device evaluation method according to this application example has a lower electrode formed on the surface of a substrate and a space on the surface of the lower electrode, and is extended in directions parallel to and opposite to each other. Measuring at least the first drive arm and the second drive arm having the same length, measuring electrical characteristics of the first drive arm and the second drive arm, and the first drive arm and the second drive arm. Calculating the median of the electrical characteristics from the electrical characteristics of each of the drive arms, and calculating the difference between the electrical characteristics of each of the first and second drive arms and the median. It is characterized by.

  According to this application example, since the first drive arm and the second drive arm are extended in directions that are parallel and opposite to each other, one of the drive arms is shifted in the extending direction of the drive arm during the manufacturing process. In this case, the other driving arm also translates in the same direction with the same amount of displacement. Thus, when the length of one drive arm is increased, the length of the other drive arm is decreased. Further, the crossing area of the lower electrode and each driving arm also becomes smaller when one becomes larger.

  As described above, when a dimensional error occurs in the length of the drive arm, the behavior of each drive arm and the electrical characteristics related to the behavior characteristic are affected. Therefore, the electrical characteristics of the first drive arm and the second drive arm are measured, the median of the electrical characteristics is calculated from the sum or difference of these electrical characteristics, the difference between each drive arm and the median is calculated, From the difference from the median, it is possible to evaluate the length error (deviation amount) of the driving arm that greatly affects the electrical characteristics.

  Since electrical characteristics can be measured more easily and with higher accuracy than actual measurements, it is troublesome to measure the dimensions of each drive arm and lower electrode of a microstructure that is manufactured using semiconductor manufacturing technology. It is possible to solve the problems that the measurement work itself is error-prone and that it depends on the accuracy of the measuring instrument itself.

  Application Example 2 The MEMS device evaluation method according to the application example described above has a space on the surface of the first drive arm, the second drive arm, and the lower electrode, and the first drive arm and the second drive. A third drive arm and a fourth drive arm extending in a direction perpendicular to the direction in which the arms extend, parallel to and opposite to each other, and having the same length, the first drive arm and the first drive arm; Measuring the electrical characteristics of each of the second driving arm, the third driving arm, and the fourth driving arm, and calculating the median of the electrical characteristics from the electrical characteristics of the first driving arm and the second driving arm. And calculating the difference between the median value and the electrical characteristics of the first drive arm and the second drive arm, and calculating the center of the electrical characteristics from the electrical characteristics of the third drive arm and the fourth drive arm. A step of calculating a value, and an electric power of each of the third driving arm and the fourth driving arm. Calculating a difference between characteristics and the median value, it will be preferable to include.

  In addition to the first driving arm and the second driving arm described above, a third driving arm and a fourth driving arm extending in a direction perpendicular to the extending direction of the first driving arm and the second driving arm are provided. Thus, the amount of deviation of the electrical characteristics due to the length error in the extending direction of the first drive arm and the second drive arm, and the electricity due to the length error in the direction orthogonal to the first drive arm and the second drive arm. It is possible to evaluate an error in two directions, that is, a characteristic deviation amount.

  Application Example 3 In the evaluation method of the MEMS device according to the application example, the electrical characteristic is a capacitance in an intersection region between the lower electrode and the first driving arm and the lower electrode and the second driving arm. It is preferable.

  The capacitance between the lower electrode and each drive arm is proportional to the area of the intersection region between the two electrodes. Therefore, when a displacement occurs in the extending direction in the driving arm extending in the same direction, if the crossing area with the lower electrode of one driving arm increases, the crossing area with the lower electrode of the other driving arm is Decrease by the same amount. Therefore, for example, by using a capacitance measuring device or the like, the capacitance of the intersection of the first and second driving arms and the lower electrode is measured, and the median value of the capacitance is calculated from the sum or difference. If the difference between the measured value and the median value of each capacitance is calculated, and further the amount of deviation of the crossing area is calculated, the amount of deviation of the capacitance can be easily determined as a length error of the drive arm and increased. Can be evaluated with accuracy.

  Application Example 4 In the MEMS device evaluation method according to the application example, it is preferable that the electrical characteristic is a resonance frequency.

  The resonance frequency of the drive arm is inversely proportional to the square of the length of the drive arm. Then, when a displacement occurs in the extending direction in the driving arms extending in the same direction, when the length of one driving arm increases, the length of the other driving arm decreases by the same amount. Therefore, for example, the resonance frequency of each drive arm is measured by using a frequency measuring device or the like, and the median value of the resonance frequencies is calculated from the sum or difference of the resonance frequencies, and the difference between the resonance frequency and the median value of each drive arm is calculated. By calculating, it is possible to evaluate the resonance frequency shift amount (error) caused by the shift in the lengths of the first drive arm and the second drive arm.

  Further, since the length of the driving arm can be calculated from the resonance frequency, the error of the resonance frequency can be evaluated as the length error of the driving arm.

  In addition, since the resonance frequency is inversely proportional to the square of the length of the driving arm, the influence of the length error on the resonance frequency appears greatly, whereas the capacitance described above is proportional to the crossing area. The length error of the first drive arm and the second drive arm can be evaluated with high accuracy.

  Application Example 5 A method of manufacturing a MEMS device according to this application example includes a step of forming a lower electrode on a surface of a substrate spread on an XY plane, and a step of forming a first anchor hole and a second anchor hole. A first anchor portion disposed in the first anchor hole, a first drive arm extending in the X direction or the Y direction continuously to the first anchor portion, and disposed in the second anchor hole Forming a second anchor portion, and a second drive arm that is continuous with the second anchor portion and extends in parallel to and opposite to the first drive arm; and Measuring electrical characteristics of the first drive arm and the second drive arm, calculating a median of electrical characteristics from the electrical characteristics of the first drive arm and the second drive arm, and the first drive. The electrical characteristics of the arm and the second drive arm Characterized in that it comprises a step of calculating the difference between the median, the.

  Here, the anchor hole means a portion for defining a position for forming an anchor portion for connecting and fixing the driving arm to the substrate. The electrical characteristics are, for example, the above-described capacitance or resonance frequency.

  According to this application example, the step of forming the lower electrode, the step of forming the first anchor hole and the second anchor hole, and the step of forming the first drive arm and the second drive arm are formed in separate steps. To do. Therefore, the positional deviation between the lower electrode and the first anchor part and the second anchor part, the positional deviation between the first anchor part and the first driving arm and the second anchor part and the second driving arm, the lower electrode and the first driving arm. In addition, positional deviation from the second drive arm may occur.

  The displacement of each drive arm corresponding to each anchor portion becomes the error of the length of each drive arm and appears as an error of the resonance frequency, and the displacement of the lower electrode and each drive arm is the intersection of the lower electrode and each drive arm. It becomes an area error and appears as a capacitance error.

  Therefore, the resonance frequency of the first driving arm and the second driving arm or the capacitance between the lower electrode and the first driving arm and the second driving arm is measured, and the median value of each is calculated, By calculating the difference from the value, it can be evaluated as an error in capacitance or an error in resonance frequency. That is, the amount of positional deviation between each anchor portion and each driving arm and between the lower electrode and each driving arm can be evaluated easily and with high accuracy.

  Application Example 6 A method of manufacturing a MEMS device according to the application example described above includes the step of forming the lower electrode, the first anchor hole and the second anchor hole, and the third anchor hole and the fourth anchor hole. , And the first driving arm, the second driving arm, a third anchor portion disposed in the third anchor hole, and the first driving arm continuous with the third anchor portion, A third driving arm extending in a direction perpendicular to an extending direction of the second driving arm, a fourth anchor portion disposed in the fourth anchor hole, and the fourth anchor portion continuously to the fourth anchor portion; Forming a fourth drive arm extending in a direction parallel to the extending direction of the third drive arm and facing each other, and the electric power of each of the first drive arm and the second drive arm Calculating the median of the electrical characteristics from the characteristics; The step of calculating the difference between the respective electrical characteristics and the median value of the first drive arm and the second drive arm, and the median value of the electrical characteristics from the electrical characteristics of the third drive arm and the fourth drive arm. Preferably, the method includes a step of calculating, and a step of calculating a difference between the electrical characteristics of the third driving arm and the fourth driving arm and the median value.

  In such a manufacturing method, a step of forming a lower electrode, a step of forming a first anchor hole, a second anchor hole, a third anchor hole, and a fourth anchor hole, a first driving arm and a second driving arm. The steps of forming the third drive arm and the fourth drive arm are formed in separate steps.

  Therefore, the displacement of the driving arm corresponding to each anchor portion becomes a length error of the driving arm, and the displacement of the lower electrode and each driving arm becomes an error of the intersection area between the lower electrode and each driving arm.

  Therefore, by measuring the capacitance or resonance frequency, calculating the median value from those measured values, and calculating the difference from the set median value, the length of the drive arm in the two directions orthogonal to the X and Y directions The error of the height and the crossing area can be evaluated by the capacitance or the resonance frequency. That is, it is possible to easily evaluate the positional deviation between each anchor portion and each driving arm and between the lower electrode and each driving arm with high accuracy.

FIG. 2 is a plan view showing the configuration of the MEMS device according to the first embodiment. Sectional drawing which shows the BB cut surface of FIG. Wafer layout diagram. FIG. 3 is a cross-sectional view showing main manufacturing steps of the MEMS device according to the first embodiment. FIG. 4 is an explanatory plan view schematically showing a shift between the first drive arm and the second drive arm according to the first embodiment. Explanatory drawing which shows the flow of the evaluation method which concerns on Embodiment 1. FIG. FIG. 4 is an explanatory diagram showing a relationship between the length of the drive arm and the resonance frequency according to the first embodiment. FIG. 6 is a plan view showing a configuration of a MEMS device according to a second embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The MEMS device of the present invention can be adapted to a resonator, a switch, a gyro sensor, an acceleration sensor, and the like. In the following embodiments, a resonator will be described as an example.
Note that the drawings referred to in the following description are schematic views in which the vertical and horizontal scales of members or portions are different from actual ones for convenience of illustration.
(Embodiment 1)

  FIG. 1 is a plan view showing a configuration of the MEMS device according to the first embodiment, and FIG. 2 is a cross-sectional view showing a BB cut surface of FIG. 1 and 2, a MEMS device 10 is formed on a substrate 20 made of silicon spread on an XY plane, a nitride layer 30 formed on the entire surface of the substrate 20, and a surface of the nitride layer 30. The first anchor base 41 and the second anchor base 42 have a conductive layer, a lower electrode 50, a first driving arm 62 and a second driving arm 64 made of polysilicon. In the present embodiment, the material of the first anchor base 41, the second anchor base 42, and the lower electrode 50 is polysilicon, and is formed in the same process.

  The first drive arm 62 is connected to the first anchor base 41 by the first anchor portion 61 and extends in the −X direction toward the second drive arm 64. The second drive arm 64 is connected to the second anchor base 42 by the second anchor part 63 and extends in the + X direction toward the first drive arm 62. That is, the first drive arm 62 and the second drive arm 64 are parallel to the X direction and extend so as to face each other. The first drive arm 62 and the second drive arm 64 have a cantilever structure having the same shape with the first anchor portion 61 and the second anchor portion 63 as fixed ends, respectively.

  The first drive arm 62 and the second drive arm 64 are formed to have the surface of the lower electrode 50 and the space 55, and the respective front end portions thereof can vibrate out of plane in the Z direction.

  A transmission circuit (inverter), a mixer (mixer), a frequency dividing circuit, and the like (not shown) are formed inside the substrate 20. The MEMS device 10 generates a potential difference between the first drive arm 62, the second drive arm 64, and the lower electrode 50, and is vibrated in the Z direction by electrostatic force.

  Here, when the MEMS device 10 is formed as designed, the length L1 of the first drive arm 62 and the length L2 of the second drive arm 64 are equal. The intersection area A1 between the first drive arm 62 and the lower electrode 50 is equal to the intersection area A2 between the second drive arm 64 and the lower electrode 50. In addition, the thickness of the 1st drive arm 62 and the 2nd drive arm 64 is represented by t, and the height of the space 55 is represented by d.

In the present embodiment, the first drive arm 62 and the second drive arm 64 are extended in a straight line in the X direction, but may be configured to extend in the Y direction. Further, the first drive arm 62 and the second drive arm 64 may be shifted from a straight line.
(Method for manufacturing MEMS device)

Then, the manufacturing method of the MEMS device 10 of this embodiment is demonstrated with reference to drawings.
FIG. 3 is a layout diagram of a wafer as a large substrate on which a plurality of MEMS devices can be arranged. The MEMS device 10 is manufactured using a semiconductor manufacturing technique by aligning a plurality of MEMS devices 10 in the X direction and the Y direction on the surface of the wafer 100. As a manufacturing process, there are a case where the wafer 100 is collectively processed at a fixed position, and a case where the wafer 100 is moved in the X direction or the Y direction for each MEMS device (illustration, each filled region).
Next, a specific method for manufacturing the MEMS device 10 will be described.

  FIG. 4 is a cross-sectional view showing main manufacturing steps of the MEMS device according to this embodiment. FIG. 4 shows a BB cut surface of FIG. 1 and 2 are also referred to.

  First, as shown in FIG. 4A, a nitride layer 30 is formed on the entire surface of the wafer 100 using film forming means such as a CVD method (Chemical Vapor Deposition) or a PVD method (Physical Vapor Deposition). A polysilicon layer serving as the lower electrode 50 and the first anchor base 41 and the second anchor base 42 is formed on the entire surface of the nitride layer 30 by using a film forming means such as a CVD method or a PVD method.

  Then, the lower electrode 50, the first anchor base 41, and the second anchor base 42 are formed by an etching method. The lower electrode 50, the first anchor base 41, and the second anchor base 42 are formed by forming the entire formation region of the plurality of MEMS devices 10 on the wafer 100 in a batch process. Accordingly, the variation in the formation position, shape, and thickness dimension of the lower electrode 50, the first anchor base 41, and the second anchor base 42 for each formation region of the plurality of MEMS devices 10 is extremely small.

  Next, as shown in FIG. 4B, the sacrificial layer 110 is formed on the entire surface of the wafer 100 including the surfaces of the lower electrode 50, the first anchor base 41, and the second anchor base 42 using the CVD method or the PVD method. To do. The thickness of the sacrificial layer 110 corresponds to the height d of the space 55 (see FIG. 2).

  Next, as shown in FIG. 4C, the first anchor hole 111 and the second anchor hole 112 are collectively formed in the entire region of the wafer 100 using means such as etching. The first anchor hole 111 is opened until reaching the first anchor base 41, and the second anchor hole 112 is opened until reaching the second anchor base 42. The first anchor hole 111 and the second anchor hole 112 correspond to the planar position and planar size of the first anchor part 61 and the second anchor part 63 (see FIG. 1).

  Next, as shown in FIG. 4D, the polysilicon layer 120 to be the first driving arm 62 and the second driving arm 64 is formed on the entire surface of the sacrificial layer 110 and the first anchor hole 111 and the second anchor hole 112. A CVD method or a PVD method is used to fill the inside.

  Subsequently, as shown in FIG. 4E, the planar shape of the first drive arm 62 and the second drive arm 64 is formed by processing in the order of the exposure process and the etching process. The exposure process for shape formation is performed independently for each of the MEMS device 10 formation regions. Therefore, after processing one MEMS device forming region in the wafer 100 shown in FIG. 3, processing of the forming region adjacent to the X direction is performed. In the present embodiment, the wafer 100 is moved in the X direction (that is, the extending direction of the first drive arm 62 and the second drive arm 64) by one formation region while the exposure apparatus (not shown) is fixed.

Subsequently, the sacrificial layer 110 is removed. This step is performed by immersing the wafer 100 in an etching solution. Therefore, the sacrificial layer 110 formed under the first driving arm 62 and the second driving arm 64 is removed, and the first driving arm 62 and the second driving arm 64 as shown in FIG. 2 are three-dimensionally formed. .
Subsequently, the wafer 100 is separated into individual MEMS devices 10 as shown in FIGS. 1 and 2 by a dicing process.

  According to such a manufacturing method, the step of forming the lower electrode 50, the step of forming the first anchor hole 111 and the second anchor hole 112, and the step of forming the first drive arm 62 and the second drive arm 64 Are formed in separate steps. The lower electrode 50, the first anchor hole 111, and the second anchor hole 112 are formed all over the wafer 100, and the exposure process for forming the first drive arm 62 and the second drive arm 64 is performed by MEMS. This is performed for each device formation region.

  Therefore, the positional deviation between the lower electrode 50 and the first anchor hole 111 and the second anchor hole 112, the positional deviation between the first anchor hole 111 and the first driving arm 62, the second anchor hole 112 and the second driving arm 64, A positional deviation between the lower electrode 50 and the first drive arm 62 and the second drive arm 64 may occur. However, since the formation of the lower electrode 50, the first anchor hole 111, and the second anchor hole 112 is performed in a state where the wafer 100 is fixed, the amount of deviation is within the range of the process standard in semiconductor manufacturing, and there is no problem.

  However, since the exposure process for forming the first drive arm 62 and the second drive arm 64 is performed by moving the wafer 100 for each formation region of the MEMS device, the first drive arm 62 and the second drive arm 64 are A length error and a deviation (error) in the crossing area with the lower electrode may occur in the moving direction of the wafer 100 for each formation region of the MEMS device in the wafer 100.

Next, the above-described deviation (error) will be described with reference to the drawings.
FIG. 5 is an explanatory plan view schematically showing the displacement between the first drive arm and the second drive arm. When the MEMS device 10 is formed according to the design value (illustrated, indicated by a two-dot chain line), the length L1 of the first drive arm 62 and the length L2 of the second drive arm 64 are equal. Further, the intersection area A1 between the first drive arm 62 and the lower electrode 50 is equal to the intersection area A2 between the second drive arm 64 and the lower electrode 50.

  Here, the case where the wafer 100 is shifted in the + X direction with respect to the exposure apparatus (mask) from the design value in the exposure process of the first drive arm 62 and the second drive arm 64 will be described. In such a case, since there is no relative displacement between the first anchor portion 61 and the second anchor portion 63, the length of the first drive arm 62 is shifted in a direction shorter than the design value length L1, If the length at this time is L3, the length is shortened by L1-L3.

  Further, the length of the second drive arm 64 is shifted in a direction longer than the design value length L2. If the length at this time is L4, the length becomes longer by L4-L2. Since the first drive arm 62 and the second drive arm 64 are formed at the same time, the amount of shift in length is equal. That is, L1-L3 = L4-L2.

  As the first drive arm 62 and the second drive arm 64 are shifted in length, an error due to the shift also occurs in the intersection area with the lower electrode 50. That is, when the length of the first drive arm 62 is shortened to L3, the intersection area is A3, and the intersection area is reduced by A1-A3. When the length of the second drive arm 64 is increased to L4, the intersection area is A4, and the intersection area is increased by A4-A2.

As described above, when a length error occurs in the first drive arm 62 and the second drive arm 64, the electrical characteristics related to the behavior and vibration characteristics of each drive arm are affected. Therefore, it is required to evaluate the dimensions of the first drive arm 62 and the second drive arm 64 with high accuracy. However, as described above, it is difficult to directly measure these deviation amounts as dimensions with high accuracy.
(Evaluation method of MEMS device)

  Therefore, an evaluation method of the MEMS device 10 according to this embodiment will be described. In this evaluation method, a deviation amount (length error) of the lengths of the first drive arm 62 and the second drive arm 64 of the MEMS device 10 manufactured by the above-described manufacturing method with respect to the design value is evaluated with high accuracy based on electrical characteristics. Related to the method.

  As an evaluation method based on electrical characteristics, a method of evaluating an error of an intersection area between the first drive arm 62 and the second drive arm 64 and the lower electrode 50 as a difference in capacitance, and a method of evaluating using a difference in resonance frequency There is. First, the capacitance will be described. The capacitance of the intersection region between the first drive arm 62 and the second drive arm 64 and the lower electrode 50 can be calculated by the following equation. Reference is made to FIG. 1, FIG. 2, and FIG.

  Here, the capacitance is C, the dielectric constant of the space 55 is ε, the crossing area is A, and the height of the space 55 is d. Since the dielectric constant ε is constant and the height d is defined by the thickness of the sacrificial layer 110, the error is negligible. Therefore, the influence of the intersection area A will be described. As shown in Equation 1, the capacitance C is proportional to the crossing area A.

  Therefore, in the state as shown in FIG. 5, the capacitance of the intersection region with the first drive arm 62 is measured, and the capacitance of the intersection region with the second drive arm 64 is measured. Then, the median value of the capacitance is calculated by ½ of the sum of both capacitances. It should be noted that ½ of the difference between both capacitances is added to the capacitance in the area of the first drive arm 62 or the capacitance in the area of the second drive arm 64 to add the center of the capacitance. A value can be calculated.

  Then, from the difference between the capacitance and the median value in the area of the first drive arm 62 or the difference between the capacitance and the median value in the area of the second drive arm 64, the first drive arm 62 is calculated using Equation 1. If the error of the intersection area of the second drive arm 64 is calculated, the error of the intersection area can be evaluated, and if this error is divided by the width of the drive arm, it can be evaluated as a length error. As described above, the length errors of the first drive arm 62 and the second drive arm 64 are equal.

  Next, a method for evaluating by the difference in resonance frequency will be described. The resonance frequency of the driving arm can be calculated by the following equation.

  Here, the resonance frequency is represented by f, the density of the drive arm is represented by ρ, the Young's modulus is represented by E, the thickness of the drive arm is represented by t, and the length of the drive arm is represented by L. The density ρ and the Young's modulus E are the same because the materials are the same, and the thickness t is the batch formation of the polysilicon layer 120 over the entire wafer. Therefore, the error for each formation region of the MEMS device is negligible. Therefore, the influence of the length L will be described. The resonance frequency f is inversely proportional to the square of the length L of the drive arm, as shown in Formula 2. Therefore, when the length L of the drive arm becomes longer, the resonance frequency becomes lower, and when the length L of the drive arm becomes shorter, the resonance frequency becomes higher. Using this characteristic, the deviation amount (length error) of the length of the drive arm is calculated.

Next, a specific method for evaluating the shift amount (length error) of the length of the drive arm based on the difference in the resonance frequency of the drive arm will be described with reference to FIG.
FIG. 6 is an explanatory diagram showing a flow of the evaluation method of the present embodiment. First, the first drive arm 62 and the second drive arm 64 are excited, and the resonance frequencies of the first drive arm 62 and the second drive arm 64 are measured using a frequency measuring device (ST10).

  Next, the resonance frequency of the first drive arm 62 and the resonance frequency of the second drive arm 64 are compared to determine whether there is a difference (ST20). When there is no difference between the respective resonance frequencies (NO), it is determined that there is no length error in the first drive arm 62 and the second drive arm 64, and the evaluation ends.

  If there is a difference between the resonance frequencies (YES), the median value of the resonance frequencies is calculated from the sum or difference of the resonance frequencies of the first drive arm 62 and the second drive arm 64 (ST30).

  Specifically, by multiplying the output signal of the first drive arm 62 and the output signal of the second drive arm 64 using a mixer (mixer), the sum or difference of those resonance frequencies is output. In the case of the sum, ½ of the sum of the output resonance frequencies is the median value. In the case of a difference, a value obtained by subtracting 1/2 of the difference between the output resonance frequencies from the higher resonance frequency is the median value, and a value added to the lower resonance frequency is the median value.

  Next, the difference between the resonance frequency of the first drive arm 62 and the median value, or the difference between the resonance frequency of the second drive arm 64 and the median value is calculated (ST40). Here, if the difference from the median is a positive value, it can be determined that there is an error in the direction in which the length of the driving arm is short, and if it is a negative value, there is an error in the direction in which the length of the driving arm is long. .

  Subsequently, the length error between the first drive arm 62 and the second drive arm 64 is calculated (ST50). Specifically, if the resonance frequencies of the first drive arm 62, the second drive arm 64, and the median value are calculated using Equation 2, the length and length of the first drive arm 62 and the second drive arm 64 are calculated. The median value can be obtained. Then, the difference between the length and the median of each vibrating arm, that is, the length error can be calculated. In this way, the evaluation is completed.

  Note that it is possible to determine in which direction the wafer 100 is moving in the X direction when forming the first drive arm 62 and the second drive arm 64 depending on whether these length errors are positive or negative. Thus, if the direction of the movement error is constant, the movement distance of the wafer 100 relative to the exposure apparatus can be corrected.

Based on the above concept, the results of creating and measuring a sample are shown in FIG.
FIG. 7 is an explanatory diagram showing the relationship between the length of the drive arm and the resonance frequency. Here, the measurement results of the resonance frequency of five prepared samples of a plurality of MEMS devices formed on one wafer are illustrated. In each sample, it is shown that the resonance frequency increases when the length of the first drive arm 62 is shortened, and the resonance frequency decreases when the length of the second drive arm 64 is increased. And if the median of the resonance frequency is calculated by the method described above based on the measured values of the resonance frequency, the median of the resonance frequency of each sample becomes constant, indicating that the above method is valid. Yes.
Note that the calculated median resonance frequency is substantially the same as the design value (target value).

  Therefore, according to the manufacturing method and the evaluation method according to the present embodiment, since the first driving arm 62 and the second driving arm 64 are extended in parallel and opposite directions, one driving arm is the driving arm. The other drive arm also translates when it is shifted in the extending direction. Thus, when the length of one drive arm is increased, the length of the other drive arm is decreased. In addition, the crossing area of the lower electrode 50 and each driving arm also decreases as one increases. The amount of deviation between the first drive arm 62 and the second drive arm 64 is the same.

  The capacitance between the lower electrode 50 and each of the first drive arm 62 and the second drive arm 64 is proportional to the area of the intersection region. Therefore, when a displacement occurs in the extending direction in the driving arm extending in the same direction, if the crossing area of the one driving arm (for example, the first driving arm 62) with the lower electrode 50 increases, the other arm The crossing area of the driving arm (for example, the second driving arm 64) with the lower electrode 50 decreases. Therefore, the capacitances of the intersecting regions of the first driving arm 62 and the second driving arm 64 and the lower electrode 50 are measured, and the median value of the capacitance is calculated from the sum or difference between the two, thereby calculating the capacitance. If the difference between the measured value and the median value is calculated, the shift amount of the crossing area can be calculated by Equation 1. Then, the length errors of the first drive arm 62 and the second drive arm 64 can be easily and highly accurately evaluated from the amount of deviation of the crossing area.

  The resonance frequency of the drive arm is inversely proportional to the square of the length of the drive arm. When the first driving arm 62 and the second driving arm 64 extending in the same direction are displaced in the extending direction, the length of one driving arm (for example, the first driving arm 62) is increased. Then, the length of the other drive arm (for example, the second drive arm 64) decreases. Therefore, the resonance frequency of each of the first drive arm 62 and the second drive arm 64 is measured, the median value of the resonance frequencies is calculated from the sum or difference of the resonance frequencies, and the median value of the resonance frequency and the resonance frequency of each drive arm. And the error of the resonance frequency and the length error of the first drive arm 62 and the second drive arm 64 can be evaluated.

  Note that the resonance frequency is inversely proportional to the square of the length of the drive arm, while the capacitance is proportional to the crossing area, so that the influence of the length error on the resonance frequency appears more prominently. The length error of the first drive arm 62 and the second drive arm 64 can be evaluated with high accuracy.

  Further, in the manufacturing method of this embodiment, the step of forming the lower electrode 50, the step of forming the first anchor hole 111 and the second anchor hole 112, and the first drive arm 62 and the second drive arm 64 are formed. Each process is formed in a separate process. Therefore, the positional deviation between the lower electrode 50 and the first anchor part 61 and the second anchor part 63, the positional deviation between the first anchor part 61 and the first drive arm 62, the second anchor part 63 and the second drive arm 64, A positional deviation between the lower electrode 50 and the first drive arm 62 and the second drive arm 64 may occur.

  In particular, in the exposure process for forming the first drive arm 62 and the second drive arm 64, the first anchor portion 61 formed in a lump on the wafer 100 is used to move the wafer 100 (in the present embodiment, move in the X direction). In addition, the first drive arm 62 and the second drive arm 64 may be displaced in the X direction due to the movement of the wafer 100 with respect to the second anchor part 63 and the lower electrode 50. The positional deviation of each driving arm corresponding to each anchor portion becomes an error in the length of each driving arm, and the length error in each driving arm becomes an error in resonance frequency and an error in capacitance.

  Therefore, the resonance frequency of the first drive arm 62 and the second drive arm 64 or the capacitance between the lower electrode 50 and the first drive arm 62 and the second drive arm 64 is measured, and the respective median values are obtained. By calculating the difference from the median, the length error of the first drive arm 62 and the second drive arm 64 can be evaluated.

These resonant frequencies and capacitances can be measured easily and with high accuracy, so they are measured against actual measurements of the dimensions of each drive arm and lower electrode of a microstructure manufactured using semiconductor manufacturing technology. Since the work itself is less prone to error and less dependent on the accuracy of the measuring instrument itself, the length error of the first drive arm 62 and the second drive arm 64 can be evaluated easily and with high accuracy.
(Embodiment 2)

  Next, Embodiment 2 will be described with reference to the drawings. In the second embodiment, the first driving arm 62 and the second driving arm 64 are extended in one direction in the X direction or the Y direction in the first embodiment described above. The drive arm is also arranged in a direction perpendicular to the extending direction of the second drive arm 64. Therefore, it demonstrates centering on a different location from Embodiment 1. FIG. In addition, the same code | symbol is attached | subjected to Embodiment 1 and a common part.

  FIG. 8 is a plan view showing the configuration of the MEMS device according to the present embodiment. In FIG. 8, the MEMS device 10 includes a substrate 20 made of silicon spread on the XY plane, a nitride layer 30 formed on the entire surface of the substrate 20, and a first formed on the surface of the nitride layer 30. Anchor base 41, second anchor base 42, third anchor base 43, fourth anchor base 44, lower electrode 50, first drive arm 62 made of polysilicon, second drive arm 64, and first drive arm The third drive arm 65 and the fourth drive arm 66 extend in a direction perpendicular to the second drive arm 62 and the second drive arm 64.

  Note that the configurations of the first drive arm 62 and the second drive arm 64 are the same as those of the first embodiment (see FIGS. 1 and 2), and thus the description thereof is omitted.

  The third drive arm 65 has a third anchor portion 67 connected to the third anchor base 43 and extends in the −Y direction toward the fourth drive arm 66. The fourth drive arm 66 has a fourth anchor portion 68 connected to the fourth anchor base 44 and extends in the + Y direction toward the third drive arm 65. That is, the third driving arm 65 and the fourth driving arm 66 are parallel to each other in the Y direction and extend so as to face each other. The third drive arm 65 and the fourth drive arm 66 each have a cantilever structure having the same shape with the third anchor portion 67 and the fourth anchor portion 68 as fixed ends.

  The third drive arm 65 and the fourth drive arm 66 may have the same configuration as that of the first drive arm 62 and the second drive arm 64 except for the extension directions. If the four drive arms 66 have the same shape (including size), the first drive arm 62 and the second drive arm 64 may have different dimensions.

Moreover, the manufacturing method of this embodiment can adapt the same method as Embodiment 1. FIG. This will be described with reference to FIG.
First, the nitride layer 30 is formed on the surface of the wafer 100, and the lower electrode 50, the first anchor base 41, the second anchor base 42, the third anchor base 43, and the fourth anchor base 44 are formed on the entire surface of the nitride layer 30. A polysilicon layer is formed.

  Then, the lower electrode 50, the first anchor base 41, the second anchor base 42, the third anchor base 43, and the fourth anchor base 44 are formed by etching. The lower electrode 50, the first anchor base 41, the second anchor base 42, the third anchor base 43, and the fourth anchor base 44 are formed by forming a plurality of MEMS device 10 formation regions in the wafer 100 in a batch process. Therefore, variations in the formation position, shape, and thickness of the lower electrode 50 and the first anchor base 41, the second anchor base 42, the third anchor base 43, and the fourth anchor base 44 for each of the formation regions of the plurality of MEMS devices 10. Is extremely small.

  Next, the sacrificial layer 110 is formed on the entire surface of the wafer 100 including the lower electrode 50 and the surfaces of the first anchor base 41, the second anchor base 42, the third anchor base 43, and the fourth anchor base 44. The anchor hole 111, the second anchor hole 112, the third anchor hole 113, and the fourth anchor hole 114 are collectively formed on the entire wafer 100.

  Next, the polysilicon layer 120 to be the first drive arm 62, the second drive arm 64, the third drive arm 65, and the fourth drive arm 66 is formed on the entire surface of the sacrificial layer 110, the first anchor hole 111, and the second anchor hole. 112, the third anchor hole 113, and the fourth anchor hole 114 are filled.

  Then, processing is performed in the order of the exposure process and the etching process, and the planar shapes of the first drive arm 62, the second drive arm 64, the third drive arm 65, and the fourth drive arm 66 are formed. The exposure process for shape formation is performed independently for each of the MEMS device 10 formation regions. Therefore, after processing one MEMS device formation region on the wafer 100 shown in FIG. 3, the exposure apparatus is fixed and adjacent to the X direction (the extending direction of the first drive arm 62 and the second drive arm 64). Processing of the formation region is performed. When the final column in the + X direction is reached, the wafer 100 is moved by one line in the + Y direction (extending direction of the third driving arm 65 and the fourth driving arm 66), and processing is performed for each region in the −X direction. Move. This process is repeated until all the formation regions are completed.

Subsequently, the sacrificial layer 110 is removed. By this step, the sacrificial layer 110 formed under the first driving arm 62, the second driving arm 64, the third driving arm 65, and the fourth driving arm 66 is removed, and these driving arms are three-dimensionally formed.
Subsequently, the wafer 100 is singulated into a single MEMS device in which the first drive arm 62, the second drive arm 64, the third drive arm 65, and the fourth drive arm 66 are formed by a dicing process.

  The MEMS device evaluation method according to the present embodiment is described by replacing the third drive arm 65 and the fourth drive arm 66 extending in the Y direction with the first drive arm 62 and the second drive arm 64 in the first embodiment. Since it can, detailed explanation is omitted.

  Therefore, according to the present embodiment, in addition to the first drive arm 62 and the second drive arm 64, the third extension extending in the direction perpendicular to the extending direction of the first drive arm 62 and the second drive arm 64. By providing the drive arm 65 and the fourth drive arm 66, the extending direction (X direction) of the first drive arm 62 and the second drive arm 64 is orthogonal to the first drive arm 62 and the second drive arm 64. It is possible to evaluate capacitance error, resonance frequency error, and length error caused by length error in two directions.

  In addition to the first drive arm 62 and the second drive arm 64, the manufacturing load is not increased by providing the third drive arm 65 and the fourth drive arm 66.

  DESCRIPTION OF SYMBOLS 10 ... MEMS device, 20 ... Board | substrate, 50 ... Lower electrode, 62 ... 1st drive arm, 64 ... 2nd drive arm.

Claims (6)

A lower electrode formed on the surface of the substrate, and at least a first driving arm and a second driving arm having a space on the surface of the lower electrode, extending in parallel to each other and facing each other, and having the same length. Have
Measuring electrical characteristics of each of the first drive arm and the second drive arm;
Calculating a median of electrical characteristics from the electrical characteristics of the first drive arm and the second drive arm;
Calculating a difference between an electrical characteristic of each of the first driving arm and the second driving arm and the median value;
A method for evaluating a MEMS device, comprising: The first driving arm, the second driving arm, and a space on the surface of the lower electrode, and parallel to each other in a direction perpendicular to the extending direction of the first driving arm and the second driving arm, and A third drive arm and a fourth drive arm extending in opposite directions and having the same length;
Measuring electrical characteristics of each of the first drive arm, the second drive arm, the third drive arm, and the fourth drive arm;
The step of calculating the median of the electrical characteristics from the electrical characteristics of the first drive arm and the second drive arm, and the difference between the electrical characteristics of the first drive arm and the second drive arm and the median A process of calculating;
Calculating a median of electrical characteristics from the electrical characteristics of the third driving arm and the fourth driving arm;
Calculating a difference between the electrical characteristics and the median value of each of the third driving arm and the fourth driving arm;
The method for evaluating a MEMS device according to claim 1, comprising:   3. The MEMS according to claim 1, wherein the electrical characteristic is a capacitance of an intersection region of the lower electrode and the first driving arm and the lower electrode and the second driving arm. Device evaluation method.   The method for evaluating a MEMS device according to claim 1, wherein the electrical characteristic is a resonance frequency. Forming a lower electrode on the surface of the substrate spread on the XY plane;
Forming a first anchor hole and a second anchor hole;
A first anchor portion disposed in the first anchor hole; a first drive arm extending in the X direction or the Y direction continuously to the first anchor portion; and disposed in the second anchor hole. Forming a second anchor portion and a second drive arm that is continuous with the second anchor portion and extends parallel to and opposite to the first drive arm;
Measuring electrical characteristics of the first drive arm and the second drive arm;
The step of calculating the median of the electrical characteristics from the electrical characteristics of the first drive arm and the second drive arm, and the difference between the electrical characteristics of the first drive arm and the second drive arm and the median And a step of calculating. A method of manufacturing a MEMS device, comprising: Forming the lower electrode;
Forming the first anchor hole, the second anchor hole, and further the third anchor hole and the fourth anchor hole;
The first drive arm, the second drive arm, a third anchor portion disposed in the third anchor hole, and an extension of the first drive arm and the second drive arm in succession to the third anchor portion. A third drive arm extending in a direction perpendicular to the direction of movement; a fourth anchor portion disposed in the fourth anchor hole; and an extension of the third drive arm continuous to the fourth anchor portion. Forming a fourth drive arm extending in a direction parallel to the direction and facing each other;
The step of calculating the median of the electrical characteristics from the electrical characteristics of the first drive arm and the second drive arm, and the difference between the electrical characteristics of the first drive arm and the second drive arm and the median A process of calculating;
Calculating a median of electrical characteristics from the electrical characteristics of the third driving arm and the fourth driving arm;
The method for manufacturing a MEMS device according to claim 5, further comprising a step of calculating a difference between an electrical characteristic of each of the third driving arm and the fourth driving arm and the median value.

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