Inertial measurement device with discharge hole structure

Abstract

An inertial measurement device for controlling surface roughness during laser sealing. The device includes a membrane having an upper surface and defining a discharge aperture extending downwardly from the upper surface. The discharge hole has a first height and a first perimeter along the first height. The discharge hole has a second height and a second perimeter extending along the second height. The first height is disposed above the second height. The first perimeter is greater than the second perimeter so as to form a shoulder portion therebetween. The shoulder portion, the first perimeter, and the first height collectively create a volume configured to control surface roughness during laser sealing of the discharge hole.

Description

Technical Field

[0001] The present disclosure relates to an inertial measurement device having a drain hole structure configured to reduce surface asperity during a laser sealing process. Background Art

[0002] In recent years, pulsed laser irradiation technology has been proposed for sealing the drain hole opening to form a sealed area in an inertial measurement unit (IMU) in order to capture the critical sensor cavity pressure within the device. The drain hole is formed by deep reactive ion etching of a silicon membrane, with a device chamber below it, which contains a vacuum level dependent micro-electromechanical system (MEMS) sensor. During the laser irradiation process, the quality of the sealed area can be significantly affected by complex process physics phenomena such as Marangoni flow and / or silicon phase transitions. The solidified silicon topology may be problematic for IMU devices. For example, surface roughness may form rough edges on the surface of the sealing area. The removal of such structures may potentially damage the quality of the component. Summary of the invention

[0003] According to one embodiment, an inertial measurement device for controlling surface roughness during laser sealing is disclosed. The device includes a membrane having an upper surface and defining a discharge hole extending downward from the upper surface. The discharge hole has a first height and a first perimeter along the first height. The discharge hole has a second height and a second perimeter extending along the second height. The first height is disposed above the second height. The first perimeter is greater than the second perimeter so as to form a shoulder portion therebetween. The shoulder portion, the first perimeter, and the first height together create a volume configured to control surface roughness during laser sealing of the discharge hole.

[0004] According to another embodiment, an inertial measurement device for controlling surface roughness during laser sealing is disclosed. The device includes a membrane having an upper surface and defining a discharge hole extending downward from the upper surface. The discharge hole has a first height and a first perimeter along the first height. The discharge hole has a second height and a second perimeter extending along the second height. The discharge hole has a third height and a third perimeter along the third height. The first height terminates at the upper surface. The second height is disposed below the first height. The third height is disposed below the second height. The first perimeter is greater than the second perimeter so as to form a first shoulder portion therebetween. The second perimeter is greater than the third perimeter so as to form a second shoulder portion therebetween. The first shoulder portion, the first perimeter and the first height and the second shoulder portion, the second perimeter and the second height together create a volume configured to control surface roughness during laser sealing of the discharge hole.

[0005] According to another embodiment, an inertial measurement device for controlling surface roughness during laser sealing is disclosed. The device includes a membrane having an upper surface and defining a discharge hole extending downward from the upper surface. The discharge hole has a first height and a first cross-section perpendicular to the first height. The discharge hole has a second height and a second cross-section perpendicular to the second height. The first height is disposed above the second height. The first cross-section is larger than the second cross-section so as to form a shoulder portion therebetween. The shoulder portion, the first cross-section, and the first height together create a volume configured to control surface roughness during laser sealing of the discharge hole. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1A Depicted is a cross-sectional view of a device formed with a silicon film.

[0007] Figure 1B A cross-sectional perspective isolated view depicting a portion of a drain hole within a device.

[0008] Figure 1C and Figure 1D Schematic side views of laser irradiation processes performed on the discharge hole opening in a molten state and a solidified state are illustrated, respectively.

[0009] Figure 2 is a graph of density versus temperature plotted for silicon.

[0010] Figure 3A is a graph that plots power ratio versus time (μs) in order to depict the laser pulse duration (ie, the length of the top of the curve).

[0011] Figure 3B is a graph depicting the Gaussian distribution of laser intensity.

[0012] Figure 4A An image depicting a drain hole seal simulated using a computational fluid dynamics (CFD) model.

[0013] Figure 4B Plotted is a comparison of the amplitude (μm) of the simulation and experimental results for melt depth, melt width, and roughness height.

[0014] Figure 5A Depicts a plan view of the spatial distribution of laser intensity according to one embodiment.

[0015] Figure 5B Plots plotting normalized intensity as a function of normalized spatial distance.

[0016] Figure 5C and Figure 5Dis a graph depicting laser pulse duration graphs for first and second examples having improved laser pulse characteristics.

[0017] Fig.6A1 and Fig.6A2 Depicted is a cross-sectional view of a first material solidification path following application of a laser heat source according to a first instance taken at a first time and at a later second time.

[0018] Figure 6A3 and Figure 6A4 Depicted is a cross-sectional view of a second material solidification path following application of a laser heat source according to a second instance taken at a first time and at a later second time.

[0019] Fig.6B1 Depicted is an enlarged cross-sectional view of a solidification path of a first material according to a first instance taken a third time after solidification.

[0020] Figure 6B2 Depicted is a cross-sectional perspective view of a first material solidification path following application of a laser heat source according to a first example taken at a third time.

[0021] Figure 6B3 Depicted is an enlarged cross-sectional view of a second cure path after curing according to the second example taken a third time.

[0022] Figure 6B4 Depicted is a cross-sectional perspective view of a second material solidification path after application of a laser heat source according to the second example taken at a third time.

[0023] Fig. 7A Graph depicting normalized intensity plotted as a function of normalized spatial distance.

[0024] Figure 7B and Figure 7C is a graph depicting laser pulse duration graphs for first and second examples having improved laser pulse characteristics.

[0025] Fig.7D Depicted is an enlarged cross-sectional view of a first material solidification path after solidification according to a first instance taken a first time.

[0026] Fig. 7E Depicted is an enlarged cross-sectional view of a second material solid object after solidification according to a first taken second example.

[0027] Fig. 8A Depicts a plan view of a laser intensity spatial distribution having an elliptical shape (eg, formed between two concentric ellipses) having a rectangular cross-section.

[0028] Figure 8BDepicts a plan view of the laser intensity spatial distribution having a square shape with rounded edges.

[0029] Figure 8C A plan view depicting the spatial distribution of laser intensity having an octagonal shape.

[0030] Fig.8D Depicted is a plan view of the spatial distribution of laser intensity with spaced apart discontinuities in the peripheral direction.

[0031] Fig. 8E Depicted is a plan view of the spatial distribution of laser intensity with spaced apart discontinuities in the radial direction.

[0032] Figure 8F Depicted is a plan view of the spatial distribution of laser intensity having spaced-apart peripheral discontinuities and spaced-apart radial discontinuities.

[0033] Fig.9A , Fig. 9B and Fig. 9C A graph depicting power ratio plotted as a function of time (μs) for the first, second and third instances associated with separate laser pulses for reducing roughness.

[0034] Fig. 10A , Fig. 10B and Fig. 10C Depicted are enlarged cross-sectional views of first, second, and third solidified objects of silicon material according to first, second, and third examples taken at a first time, respectively.

[0035] Fig.11A and 11B A diagram depicting the positions of the secondary laser pulses at their starting moments for the second and third examples.

[0036] Fig. 12A , Fig. 12B , Fig. 12C , Fig.12D , Fig.12E and Fig.12D Plotted are graphs of power ratio plotted as a function of time (μs) for first, second, third, fourth, fifth, and sixth instances respectively associated with laser pulses having multiple laser pulse regions (eg, two or more) for reducing surface roughness.

[0037] Fig.13A Depicted is a membrane material defining a drainage hole having a constant diameter along the length of the drainage hole.

[0038] Fig. 13B Depicted is a membrane material defining a drainage hole having a variable diameter along the length of the drainage hole.

[0039] Fig.14A and Fig. 14B Describe according to Fig.13A and Fig. 13B Magnified cross-sectional views of first and second solidified products of silicon films of first and second examples illustrating variable diameter drainage holes to reduce surface roughness.

[0040] Fig.15A Depicted are cross-sectional views of first, second, and third drain holes having first, second, and third diameters, respectively, in an upper region of a silicon membrane.

[0041] Fig. 15B A cross section AA' taken at the height of the silicon membrane is depicted.

[0042] Fig. 15C , Fig.15D and Fig.15E Various AA' cross-sectional shapes of drain holes formed according to one or more embodiments are depicted. DETAILED DESCRIPTION

[0043] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments can take different or alternative forms. The drawings are not necessarily to scale; some features can be exaggerated or reduced in order to illustrate the details of specific parts. Therefore, the specific structural and functional details disclosed herein should not be understood as limitations, but only as a representative basis for teaching those skilled in the art to use the embodiments differently. As will be understood by those skilled in the art, various features shown or described with reference to any one of the drawings can be combined with features shown in one or more other drawings to produce embodiments that are not explicitly shown or described. The combination of the features shown provides representative embodiments for typical applications. Various combinations or modifications of features are consistent with the teachings of the present disclosure, however, can be expected to be used in specific applications or embodiments.

[0044] Except in the examples, or where otherwise explicitly indicated, all numerical parameters in this description indicating the amount of materials or conditions of reaction and / or use should be understood as modified by the word "about" in describing the broadest scope of the invention. Practice within the stated numerical limits is generally preferred. In addition, unless expressly stated to the contrary: Percents, "parts of..." and ratios are by weight; the term "polymer" includes "oligomers," "copolymers," "terpolymers," and the like; descriptions of groups or classes of materials suitable or preferred for a given purpose in connection with the present invention imply that mixtures of any two or more of the members of the group or class are equally suitable or preferred; molecular weights for any polymer refer to the number average molecular weight; descriptions of ingredients in chemical terms refer to the ingredients at the time of addition of any combination specified in this description, and do not necessarily exclude chemical interactions among the ingredients of the mixture once mixed; the first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein, and applies mutatis mutandis to the common grammatical variations of the originally defined abbreviation; and, unless expressly stated to the contrary, measurements of properties are determined by the same techniques as referenced before or after for the same property.

[0045] The present invention is not limited to the specific embodiments and methods described below, as specific parts and / or conditions may of course vary.In addition, the terminology used herein is only for the purpose of describing embodiments of the present invention, and is not intended to be limiting in any way.

[0046] As used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a part in the singular is intended to include a plurality of parts.

[0047] The term "substantially" may be used herein to describe disclosed or claimed embodiments. The term "substantially" may modify a value or related characteristic disclosed or claimed in the present disclosure. In such examples, "substantially" may mean that the value or related characteristic it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the value or related characteristic.

[0048] In one or more embodiments, a method for reducing the surface roughness of the sealing area in the laser sealing of silicon membranes is disclosed. One or more embodiments rely on a computational fluid dynamics (CFD) model to simulate the laser used in the silicon membrane sealing process. Complex process physics phenomena, such as surface tension and / or solid volume shrinkage, are considered in the CFD model. Temperature-dependent material properties, such as density, conductivity, specific heat and / or surface tension coefficient can be included in the CFD model to improve simulation accuracy.

[0049] In one or more embodiments, continuous laser pulses with defined primary and secondary pulse regions are used to promote the reduction of surface roughness. The spatial distribution of laser intensity of the primary and / or secondary pulse regions can be a donut shape with a rectangular or Gaussian cross section. The power of the secondary laser pulse region can be a percentage (e.g., in the range of 10% to 60%) less than the power of the primary laser pulse region.

[0050] In one or more embodiments, in a system using first and second independent and separate time laser pulse regions, the secondary laser pulse can be applied with a suitable time interval (e.g., the time value between the primary laser pulse and the supplemental laser pulse) to reduce the surface roughness. The surface roughness reduction effect can be improved by reducing the time interval. Conversely, the surface roughness reduction effect can be reduced by increasing the time interval.

[0051] In one or more embodiments, variable drain hole diameter or perimeter may be used to reduce surface roughness.

[0052] Laser pulse irradiation techniques can be utilized to seal the exhaust orifice opening in an inertial measurement unit (IMU) configured to capture critical sensor cavity pressure within the device. Figure 1A A cross-sectional view of a device 10 formed of a material 12, such as a silicon film, is depicted. The material 12 defines a device chamber 14 and a drain hole 16. The drain hole 16 terminates at a drain hole opening 18. The drain hole 16 extends between the device chamber 14 and the drain hole opening 18. Figure 1B A cross-sectional perspective isolated view of a portion of a drain aperture 16 within a device 10 is depicted. Figure 1B A seal 20 is depicted which is configured to seal the drain hole opening 18. The seal area 18 is formed via a laser irradiation process.

[0053] When material 12 is a silicon film, drain hole 16 is formed by chemical etching of the silicon (Si) film, beneath which is device cavity 14, which contains a pressure sensitive micro-electromechanical system (MEMS) sensor. During the laser irradiation process, the silicon in the sealing area melts, flows and re-solidifies, during which the seal quality can be significantly affected by complex process physics phenomena (such as Marangoni flow and / or Si phase transitions). As the molten silicon solidifies, the volume increases, thereby reducing the density, resulting in the formation of peak surface roughness. Peak surface roughness can be problematic for the IMU device in the case of an adjacent device built on top of the IMU.

[0054] Figure 1C and Figure 1D Schematic side views of the laser irradiation process performed on the drain hole opening 18 in a molten state and a solidified state are illustrated respectively. The laser irradiation process forms a seal 20 having a Figure 1D The surface anomaly shown in the figure. Figure 1C , a laser pulse 24 having a pulse duration is used to irradiate the top surface 26 of the silicon film adjacent to the discharge hole 16. The material under the irradiated area 28 begins to melt and flow to fill the discharge hole 16. After the laser pulse 24 is turned off, as shown in FIG. Figure 1D As shown in FIG. 1 , the molten silicon solidifies and seals the drain hole 16. However, Figure 1D As shown in FIG. 2 , surface roughness 22 is formed on the seal 20. The reason for the formation of the surface roughness may be based on the specific physical properties of the silicon material (eg, the silicon material has a liquid density greater than a solid density around its melting temperature).

[0055] Figure 2 is a graph of density and temperature for silicon. Figure 2 As shown in the figure, silicon has a liquid density greater than solid density around its melting temperature. The volume contraction and expansion of silicon material during melting and solidification can ultimately contribute to the formation of surface roughness.

[0056] One proposal involves mechanically removing the cured silicon roughness. However, mechanical removal may present a risk of failure of the seal by creating a fragile seal that seals the silicon vent hole.

[0057] In one or more embodiments, multi-physics digital simulation is used to study laser irradiation and melting of silicon materials for optimization of processing parameters to reduce or limit the surface roughness of solidification. One or more embodiments thus present novel laser irradiation methods or mechanisms to reduce or eliminate the surface roughness of solidification in the IMU manufacturing process.

[0058] The multi-physics CFD model characterizes the complex thermal fluid phenomena in the drain hole sealing process. In one or more embodiments, the model includes a stationary laser irradiation heat source, a solid to liquid phase transition, a solidification volume change, surface tension due to Marangoni flow, vapor pressure, and / or temperature dependent thermal fluid properties. The geometric information of the IMU silicon membrane with the drain hole (e.g. Figure 1B Regions of interest in the image may also be included.

[0059] A variant simulation for the CFD model can be performed using one or more of the following process conditions: (1) laser irradiation power to the material surface; (2) silicon film thickness; (3) film temperature; and (4) discharge hole diameter, 10 μm. The laser irradiation power to the material surface can be 15 to 500 W. The silicon film thickness can be in the range of 50 to 300 μm. The discharge hole diameter can be 4 to 25 μm.

[0060] Figure 3A and Figure 3BDepicts laser irradiation characteristics, collected from a laser sealing setup. Figure 3A is a graph that plots power ratio versus time (μs) in order to depict the laser pulse duration (ie, the length of the top of the curve). Figure 3B is a graph of normalized intensity plotted as a function of normalized spatial distance. Figure 3B is a graph depicting the Gaussian distribution of laser intensity.

[0061] Figure 4A Depicted is an image of a vent hole seal 50 simulated using a CFD model of an embodiment. The vent hole seal 50 includes a sealed vent hole 52. The vent hole seal 50 includes a melt depth D, a melt width W, and a roughness height H. Figure 4B Plots the comparison of simulation results and experimental results for the magnitude (μm) of melt depth, melt width, and roughness height. Figure 4B In the figure, Figure 4A The simulated solidified material properties have a reasonable consensus with the experimental measurements. Figure 4A and Figure 4B The CFD model of one or more embodiments can be used to characterize the formation of surface roughness during the laser sealing process. The CFD model can further be used to investigate and optimize the sealing quality.

[0062] In one or more embodiments, the laser shot shape and pulse duration may be optimized to reduce surface roughness.The laser shot shape may be a laser intensity distribution having a donut shape (eg, formed between two concentric circles) with a rectangular cross-section. Figure 5A Depicted is a plan view of a laser intensity spatial distribution 100 according to one embodiment. Figure 5A The dashed line 102 represents Figure 5B The x-axis of the graph shows the normalized spatial distance, and the Figure 5A The laser intensity spatial distribution obtained by the dashed line 102. In the laser irradiation area, for example, a donut shape formed between two concentric circles, which shows the shape of a rectangular cross section. The normalized spatial distance is -1 on the left side of the dashed line 102 and extends to +1 on the right side of the dashed line 102. Figure 5B A graph depicting normalized intensity plotted as a function of normalized spatial distance. As can be seen, Figure 5B The intensities of the rectangular shapes between -0.5 and -0.6 and between 0.5 and 0.6 are illustrated.

[0063] In one or more embodiments, modification of one or more laser pulse characteristics of a donut shape, rectangular cross-section laser intensity profile may result in reduced surface roughness. Figure 5C and Figure 5Dis a graph depicting laser pulse duration graphs for the first and second examples using modified laser pulse characteristics. Figure 5C and Figure 5D As shown, although the first and second examples have the same laser pulse duration for primary laser pulses 150 and 152 , respectively, the laser intensity profiles of the first and second examples are different, where the secondary laser pulse 154 has less power.

[0064] Fig.6A1 and Fig.6A2 Depicts a cross-sectional view of a solidification path of a first material after application of a laser heat source according to a first instance taken at a first time and at a later second time. Dashed line 200 represents the center of symmetry of the discharge hole of the first instance. Reference numeral 202 represents the discharge hole at the first and second times. Region 204 represents a first region above the melting point of the silicon material at the first time. Region 206 represents a second region above the melting point of the silicon material at the second time. Region 208 represents a first region below the melting point of the silicon material at the first time. Region 210 represents a second region below the melting point of the silicon material at the second time. As in Fig.6A1 and Fig.6A2 As shown by arrows in the figure, the second region above the melting point has a smaller area than the first region above the melting point as the silicon material solidifies, and the first region below the melting point has a smaller area than the second region below the melting point as the silicon material solidifies. The arrows represent the solidification path of the silicon material.

[0065] Figure 6A3 and Figure 6A4 Depicts a cross-sectional view of a solidification path of a second material after application of a laser heat source according to a second instance taken at a first time and at a later second time. Dashed line 212 represents the center of symmetry of the discharge hole of the second instance. Reference numeral 214 represents the discharge hole at the first and second times. Region 216 represents a first region above the melting point of the silicon material at the first time. Region 218 represents a second region above the melting point of the silicon material at the second time. Region 210 represents a first region below the melting point of the silicon material at the first time. Region 212 represents a second region below the melting point of the silicon material at the second time. As in Fig.6A1 and Fig.6A2 As shown by arrows in the figure, the second region above the melting point has a smaller area than the first region above the melting point as the silicon material solidifies, and the first region below the melting point has a smaller area than the second region below the melting point as the silicon material solidifies. The arrows represent the solidification path of the silicon material.

[0066] from Fig.6A1 , Fig.6A2 , Figure 6A3 and Figure 6A4It is observed that the first example follows a solidification path from the outside to the center relative to the top surface of the silicon material, while the second example follows a solidification path from the center to the outside relative to the top surface of the silicon material. The energy input from the secondary laser pulses contributes to the change in the solidification path of the second example. The addition of the secondary laser pulse input creates a high temperature region around the periphery of the melt pool, which promotes the peripheral area of ​​the melt pool to cool slower than the central area. The different types of solidification paths of the first example and the second example result in completely different surface morphologies. The first example Fig.6A2 The surface peak 224 of the second example Figure 6A4 The substantial reduction shown is in the range of 20% to 90%.

[0067] Fig.6B1 Depicted is an enlarged cross-sectional view of a solidification path of a first material according to a first instance taken a third time after solidification. Figure 6B2 Depicted is a cross-sectional perspective view of a first material solidification path after application of a laser heat source according to the first example taken a third time. Fig.6B1 and Figure 6B2 Region 226 is a melted and fully solidified region (eg, the material has gone through the entire melting and solidification process). Fig.6B1 Region 228 illustrates a portion of the fully cured region, which represents a first surface roughness. Figure 6B3 Depicted is an enlarged cross-sectional view of a second material solidification path according to the second instance taken a third time after solidification. Figure 6B4 Depicted is a cross-sectional perspective view of a second material solidification path after application of a laser heat source according to the second example taken a third time. Figure 6B3 and Figure 6B4 Region 230 is a melted and fully solidified region. Figure 6B3 The area 232 of FIG. 1 illustrates a portion of the fully cured area, which represents a second surface roughness. The height of the second surface roughness is significantly smaller than the height of the first surface roughness.

[0068] In another embodiment, the laser shot shape may be a donut-shaped laser intensity distribution with a Gaussian cross section. Fig. 7A A graph depicting normalized intensity plotted as a function of normalized spatial distance. As can be seen, Fig. 7A Gaussian shaped cross sections are shown between approximately -0.9 and -0.4 and between approximately 0.4 and 0.9. Fig. 7A The normal distribution of the normalized laser intensity about each Gaussian-shaped cross section is illustrated.

[0069] In one or more embodiments, modification of one or more laser pulse characteristics of a donut shape, a Gaussian cross-section, a laser intensity profile may result in a reduction in surface roughness. Figure 7B and Figure 7C is a graph depicting laser pulse duration graphs for the first and second examples with modified laser pulse characteristics. Figure 7B and Figure 7C As shown, while the first example uses only primary laser pulses, the second example uses secondary laser pulses having less power than the primary laser pulses.

[0070] Fig.7D Depicted is an enlarged cross-sectional view of a first material solidification path after solidification according to a first instance taken a first time. Fig. 7E Depicted is an enlarged cross-sectional view of a second material solidification path according to a first take of a second instance after solidification. Fig.7D Region 250 is a first instance of a melted and fully solidified region (eg, material that has gone through the entire melting and solidification process). Fig. 7E Region 252 is the melted and fully solidified region of the second example. Fig.7D Region 254 illustrates a portion of the fully cured region, which represents the first surface roughness (ie, the area above line 255). Fig. 7E Region 256 illustrates a portion of the fully cured region, which represents a second surface roughness (ie, the area above line 257). The height of the second surface roughness is significantly less than the height of the first surface roughness. The significant reduction may be in the range of 20% to 90%.

[0071] although Figure 5A While depicting a donut shaped laser intensity profile configured to reduce surface roughness, one or more other embodiments may include a different laser intensity profile shape. Fig. 8A A plan view of a laser intensity spatial distribution 260 having an elliptical shape (e.g., formed between two concentric ellipses) is depicted, which has a rectangular cross-section. The elliptical shape has a major axis and a minor axis. In one or more embodiments, the length of the major axis and the length of the minor axis are differentiated by one of the following values ​​or in a range of two of the following values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20%. Figure 8B A plan view of a laser intensity spatial distribution 262 is depicted having a square shape with rounded edges. Other rectangular shapes are contemplated in one or more embodiments. Other polygons may also be used as the shape for the laser intensity spatial distribution. For example, Figure 8C A plan view of a laser intensity spatial distribution 264 is depicted having an octagonal shape. Fig. 8A , Figure 8B and Figure 8C The shaded area on the graph indicates the laser energy.

[0072] although Figure 5A , Fig. 8A , Figure 8B and Figure 8C A continuous distribution of laser energy is depicted, in other embodiments the distribution of laser energy may be discontinuous. Fig.8D , Fig. 8E ,and Figure 8F Depicted is a discontinuous distribution of laser energy in accordance with one or more embodiments. Fig.8D Depicted is a plan view of a laser intensity spatial distribution 266 having spaced apart discontinuities 268 in a peripheral direction. The spaced apart discontinuities 268 may be equally spaced; sequentially unequally spaced; randomly unequally spaced; or a combination thereof. Fig. 8E Depicted is a plan view of a laser intensity spatial distribution 270 having spaced apart discontinuities 272 in a radial direction. The spaced apart discontinuities 272 may be equally spaced; sequentially unequally spaced; randomly unequally spaced; or a combination thereof. Figure 8F A plan view of a laser intensity spatial distribution 274 having spaced-apart peripheral discontinuities 276 and spaced-apart radial discontinuities 278 is depicted. Fig.8D , Fig. 8E and Figure 8F The shaded area on indicates the laser energy. Any of the discontinuous laser energy profiles can be used with any of the laser profile shapes disclosed in one or more embodiments.

[0073] In one or more embodiments, the laser energy spatial distribution is stationary (e.g., stationary in the x, y, and z directions). In other embodiments, the laser energy spatial distribution (e.g., primary and / or secondary pulses) may have movement (e.g., radial movement in the x and y directions). The movement distance may be limited to a measured offset percentage relative to the laser distribution shape. For example, the movement distance may be an offset percentage of one of the following values ​​or in a range of any two of the following values: 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10%. For example, the movement distance may be equal to or less than 10% of the laser donut diameter. Figure 8G A top view of the laser intensity spatial distribution 280 is depicted, with arrows 282 depicting the magnitude of the shift in the radial direction.

[0074] One or more of the above embodiments demonstrates an example of continuous laser pulses with defined primary and secondary pulse regions promoting roughness reduction. In another embodiment, two or more separate laser pulses can reduce roughness. Any of the laser spatial distribution shapes and continuous / discontinuous portions can be adopted to the embodiments utilizing two or more separate laser pulses. Fig.9A , Fig. 9B and Fig. 9CA graph depicting power ratio plotted as a function of time (μs) for the first, second and third instances associated with separate laser pulses for reducing roughness. Fig.9A The main pulse area is shown, and there is no secondary pulse area. Fig. 9B The primary pulse region and the secondary pulse region are shown with a first interval therebetween. Fig. 9B As shown in the figure, the primary pulse region has a shorter duration than the secondary pulse region, and the primary pulse region has a higher power than the secondary pulse region. Fig. 9C The main pulse area and the secondary interval between them are shown. Fig. 9C As shown in FIG. 1 , the primary pulse region has a shorter duration than the secondary pulse region, and the primary pulse region has a higher power than the secondary pulse region. The second interval is longer than the first interval.

[0075] Fig. 10A , Fig. 10B and Fig. 10C Depicted are enlarged cross-sectional views of first, second, and third solidified objects of silicon material according to first, second, and third examples taken at a first time, respectively. Fig. 10A Region 300 is a first instance of a melted and fully solidified region (eg, material that has gone through the entire melting and solidification process). Fig. 10B Region 302 is the melted and fully solidified region of the second example. Fig. 10C Region 304 is the melted and fully solidified region of the third example. Fig. 10A Region 306 illustrates a portion of the fully cured region, which represents a first surface roughness (ie, the area above line 312). Fig. 10B Region 308 illustrates a portion of the fully cured region, which represents the second surface roughness (ie, the region above 314). Fig. 10C Region 310 illustrates a portion of the fully cured region, which represents a third surface roughness. The height of the second surface roughness may be significantly less than the heights of the first and third surface roughnesses. The significant reduction may be in the range of 20% to 90%.

[0076] If through Fig. 10B and Fig. 10C It can be seen that the secondary pulse region separated from the primary pulse region reduces the height of the surface roughness. Fig. 9B Compared with the time interval shown in the figure Fig. 10C The time intervals shown in the figure are smaller, and Fig. 10B Compared with the time interval Fig. 10C The time interval between the primary laser pulse and the secondary laser pulse is more favorable for reducing the surface roughness. In one or more embodiments, the time interval between the primary laser pulse and the secondary laser pulse is carefully selected, because a relatively large time interval can reduce the surface roughness. Fig. 10B In the second example shown in FIG. 1 , at the start of the secondary laser pulse, the secondary pulse laser is applied to the melting region of the silicon material. Fig. 10C In the third example illustrated in FIG, due to the longer cooling period (e.g., at least two times longer), the secondary laser pulse is applied within the resolidified region of the silicon material at the time of the start of the secondary laser pulse, and thus has minimal effect on the roughness height reduction.

[0077] Fig.11A and Fig. 11B A diagram depicting the positions of the secondary laser pulses at their starting moments for the second and third examples. Fig.11A As shown in FIG. 1 and related to the second example, at the time of the start of the secondary laser pulse 350, the secondary laser pulse 350 is applied within the melting region 352 of the silicon material. The laser irradiation position is at the edge of the melting region 352, thereby moving the melted material from the center of the melting region 352 to its edge. This movement of the melted material reduces the surface roughness. Fig. 11B As shown in FIG. 1 , and in relation to the third example, at the moment of initiation of the secondary laser pulse 354, the secondary laser pulse 354 is applied outside the melt region 356, rather than in the resolidified region. This not only does not reduce the roughness of the illumination through the melted region, it can also cause the generation of additional surface roughness at the location of the secondary laser pulse 354 outside the melt region 356.

[0078] The time interval can also be expressed as a ratio between the duration of the primary laser pulse and the time interval. In one or more embodiments, the ratio of the time interval to the duration of the primary laser pulse can be any one of the following ratios or in a range of any two of the following ratios: 0.01:1, 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, and 0.6:1. As another ratio related to one or more embodiments, the ratio of the secondary laser pulse to the primary laser pulse can be any one of the following ratios or in a range of any two of the following ratios: 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2.5:1, or 2:1.

[0079] In one or more embodiments, multiple continuous or discontinuous laser pulses with defined pulse regions (eg, two or more) may be used to reduce surface roughness. Fig. 12A , Fig. 12B , Fig. 12C , Fig.12D , Fig.12E and Fig.12FA graph depicting power ratio as a function of time (μs) for first, second, third, fourth, fifth, and sixth instances of laser pulses associated with a plurality of laser pulse regions (e.g., two or more) for reducing surface roughness, respectively. In one embodiment, the main laser pulse region may include a plurality of discrete laser pulses having the same laser power (e.g., 100% laser power) with relatively short time intervals between consecutive laser pulses (e.g., each time interval is about 1% to 2% relative to the entire duration of the main laser pulse region). The plurality of discrete laser pulses may also have different durations. Fig. 12A A primary laser pulse region with multiple discrete laser pulses is illustrated. In another embodiment, the secondary laser pulse region may include multiple discrete laser pulses with the same laser power (e.g., 25% laser power) or different laser powers with relatively short time intervals between consecutive laser pulses (e.g., each time interval is about 1% to 2% relative to the entire duration of the secondary laser pulse region). Fig. 12B The secondary laser pulse region is shown as having multiple discrete laser pulses. In another embodiment, both the primary and secondary laser pulse regions may have multiple discrete laser pulses, e.g. Fig. 12C Medium picture.

[0080] In certain embodiments, the plurality of discrete laser pulses may have different laser power levels and / or durations. Fig.12D The main laser pulse region is shown comprising a plurality of discrete laser pulses having varying power levels. Fig.12E The illustration shows a secondary laser pulse region comprising a plurality of discrete laser pulses having varying power levels. Fig.12F 41 , 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 , 52, 53, 54, 55, 56, 57, 58, 59, and 60%.

[0081] In one or more embodiments, variable drain hole diameter can be used to mitigate surface roughness. Figure 5DA second example disclosed herein utilizes where the laser pulse is a donut shape with a primary and secondary pulse. Any of a continuous or discontinuous shaped laser profile may be used in accordance with the variable discharge hole diameter embodiment.

[0082] Fig.13A and 13B Schematic views depicting first and second examples of laser sealed drain holes in conjunction with silicon membranes. Fig.13A Depicted is a film material 400 defining a drainage hole 402 having a constant diameter along the length of the drainage hole 402 . Fig. 13B Depicts a membrane material 404 defining a drain hole 406 having a variable diameter along the length of the drain hole 408. The drain hole 406 includes a first diameter section 408 and a second diameter section 410. The first diameter section 408 extends between the drain hole opening 412 and the second diameter section 410. The second diameter section 410 extends between the first diameter section 408 and the device chamber (not shown). The transition between the first diameter section 408 and the second diameter section 410 forms a shoulder section 414 that is cylindrical and shaped and has a width of the difference between the diameters of the first diameter section 408 and the second diameter section 410. The first diameter section 408 is larger than the second diameter section 410 by a percentage. The percentage may be any one of the following values ​​or in a range of any two of the following values: 30%, 35%, 40%, 45%, 50%, and 55%. The length of the first diameter section 408 may be equal to the diameter of the first diameter section 408. In another embodiment, the enlarged section of the drain hole may taper from a larger diameter to the diameter of the base diameter drain hole portion.

[0083] Fig.14A and Fig. 14B Describe according to Fig.13A and Fig. 13B Magnified cross-sectional views of first and second solidified products of silicon films of first and second examples illustrating variable diameter drainage holes to reduce surface roughness. Fig.14A Region 450 is a first instance of a melted and fully solidified region (eg, material that has gone through the entire melting and solidification process). Fig. 14B Region 452 is the melted and fully solidified region of the second example. Fig.14A Region 454 illustrates a portion of the fully cured region, which represents a first surface roughness (ie, the area above line 456 , which has a height depicted by arrow 458 ). Fig. 14BThe area 460 of FIG. 4 illustrates a portion of the fully solidified area, which represents a second surface roughness (i.e., the area above line 462, which has a height depicted by arrow 464). The height of the second surface roughness is less than the height of the first surface roughness, thereby supporting the enlarged diameter portion adjacent to the drain hole opening to accommodate additional molten material and reduce the surface roughness on the solidified object. The reduction may be in the range of 15% to 30%.

[0084] In one or more embodiments, two or more drainage holes with variable diameters may be employed to reduce surface roughness. Fig.15A A cross-sectional view of a first drain hole 500, a second drain hole 502, and a third drain hole 504 having a first diameter, a second diameter, and a third diameter, respectively, is depicted in an upper region of a silicon film 506. The first drain hole 500, the second drain hole 502, and the third drain hole 504 are configured to create a volume to accommodate a solidified material under direct laser irradiation. The first diameter, the second diameter, and the third diameter may be greater than any of the following percentages of the initial drain hole diameter (e.g., diameter 508), or greater than any of the following percentages in the range of any two of the following percentages: 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, and 150%. The initial drain hole diameter may be any of the following values ​​or in the range of any two of the following values: 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 μm. The total height of all the drain holes may be any one of the following values ​​or a range of any two of the following values: 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 and 25 μm.

[0085] The cross-section of the discharge hole formed into the silicon membrane at the height of the silicon membrane may have a substantially circular shape. Fig. 15B A cross section AA′ taken at the height of the silicon membrane 506 is depicted. Fig. 15C , Fig.15D and Fig.15E Various AA' cross-sectional shapes of drain holes formed according to one or more embodiments are depicted. Fig. 15C An elliptical shape 510 (eg, a substantially elliptical shape) is depicted. Fig.15D A square shape 512 is depicted (eg, a substantially square shape with rounded corners). Fig.15E A rectangular shape 514 (eg, a substantially rectangular shape) is depicted.

[0086] In one or more embodiments, a CFD model is used to simulate the laser silicon membrane sealing process for an IMU sensor. The CFD model takes into account process physics phenomena such as surface tension and solid volume shrinkage. Additionally, temperature-dependent material properties such as density, conductivity, specific heat, and surface tension coefficient are considered in the CFD model for accurate simulation.

[0087] As illustrated in one or more embodiments above in relation to continuous laser pulses, the combination of a primary laser pulse and a secondary laser pulse can reduce the surface roughness height. The intensity spatial division can be a donut shape with a rectangular or Gaussian cross section. The power of the secondary laser power can be a percentage less than the power of the primary laser source. The percentage can be in the range of 20% to 60%.

[0088] In one or more embodiments, using continuous laser pulses, supplemental (e.g., secondary) laser pulses can reduce surface roughness height. The laser intensity spatial distribution can be a donut shape (or other laser shapes as described herein) with a rectangular or Gaussian cross section. The supplemental laser power can be less than the main laser power, for example 10% to 60%.

[0089] In one or more embodiments, two separate laser pulses may be utilized, where the application of a supplemental laser pulse with a suitable time interval (time value between the primary and supplemental laser pulses) can help reduce the surface roughness height. However, the greater the time interval, the less impact the surface roughness height reduction has. The primary and secondary laser pulses may include multiple independent laser shots.

[0090] In one or more embodiments, a variable drain hole diameter configuration may be utilized to reduce surface roughness height. In one or more embodiments, multiple drain holes with varying diameters may help reduce surface roughness, and the drain hole cross-section may not have a perfectly circular shape.

[0091] The following applications are related to the present application: US patent application serial number 17 / 863659 (RBPA0386PUS), filed on July 13, 2022, and US patent application serial number 17 / 863665 (RBPA0395PUS), filed on July 13, 2022, each of which is incorporated herein by reference in its entirety.

[0092] The process, method or algorithm disclosed herein can be delivered to / implemented by a processing device, a controller or a computer, which can include any existing programmable electronic control unit or a dedicated electronic control unit. Similarly, the process, method or algorithm can be stored as data and instructions executed by a controller or a computer in many forms, including but not limited to information permanently stored on a non-writable storage medium (such as a ROM device) and information variably stored on a writable storage medium (such as a floppy disk, a tape, a CD, a RAM device and other magnetic or optical media). The process, method or algorithm can also be implemented as a software executable object. Alternatively, the process, method or algorithm can be implemented in whole or in part using suitable hardware parts (such as an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), a state machine, a controller or other hardware parts or devices or a combination of hardware, software and firmware parts).

[0093] Although the exemplary embodiments are described above, it is not expected that these embodiments describe all possible forms included by the claims. The words used in the specification are descriptive words rather than restrictions, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously described, the features of the various embodiments can be combined to form other embodiments of the invention, which may not be explicitly described or displayed. Although the various embodiments can be described as providing advantages or being superior to other embodiments or prior art embodiments with respect to one or more desired characteristics, those skilled in the art will appreciate that one or more features or characteristics can be included to achieve the desired overall system characteristics, which depends on the specific application and implementation. These characteristics can include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Thus, with respect to any embodiment described as being less desirable than other embodiments or prior art embodiments with respect to one or more characteristics, these embodiments are not outside the scope of the present disclosure and can be desirable for a specific application.

Claims

1. An inertial measurement device for controlling surface roughness during laser sealing, the device comprising: A membrane having an upper surface and defining a drain hole extending downwardly from the upper surface, the drain hole having a first height and a first perimeter along the first height, the drain hole having a second height and a second perimeter extending along the second height, the first height being disposed above the second height, the first perimeter being greater than the second perimeter so as to form a shoulder portion between the first perimeter and the second perimeter, the shoulder portion, the first perimeter, and the first height together creating a volume configured to control surface roughness during laser sealing of the drain hole. 2 . The inertial measurement unit of claim 1 , wherein the first perimeter is a first circular shape perimeter having a first diameter, and the second perimeter is a second circular shape perimeter having a second diameter, the first diameter being greater than the second diameter by a percentage. The inertial measurement unit of claim 2 , wherein the percentage is 30% to 55%. The inertial measurement device according to claim 2 , wherein the second diameter is 4 to 25 μm. The inertial measurement unit of claim 2 , wherein the first height is substantially equal to the first diameter. The inertial measurement device of claim 1 , wherein the first perimeter tapers from the wide end to the narrow end. 7 . The inertial measurement unit of claim 1 , wherein the drain hole includes a seal located at the upper surface and having a sealing surface having a controlled surface roughness characteristic of a reduced surface roughness height. 8 . The inertial measurement device of claim 1 , wherein the first height is 15 to 50 μm.

9. The inertial measurement device of claim 1, wherein the membrane is a silicon membrane.

10. An inertial measurement device for controlling surface roughness during laser sealing, the device comprising: A membrane having an upper surface and defining a drain hole extending downwardly from the upper surface, the drain hole having a first height and a first perimeter along the first height, the drain hole having a second height and a second perimeter extending along the second height, the drain hole having a third height and a third perimeter along the third height, the first height terminating at the upper surface, the second height being disposed below the first height, the third height being disposed below the second height, the first perimeter being greater than the second perimeter so as to form a first shoulder portion between the first perimeter and the second perimeter, the second perimeter being greater than the third perimeter so as to form a second shoulder portion between the second perimeter and the third perimeter, the first shoulder portion, the first perimeter and the first height, and the second shoulder portion, the second perimeter and the second height together creating a volume configured to control surface roughness during laser sealing of the drain hole.

11. The inertial measurement device of claim 10, wherein the first perimeter is a first circular shape perimeter having a first diameter, the second perimeter is a second circular shape perimeter having a second diameter, the third perimeter is a third circular shape perimeter having a third diameter, the first diameter is greater than the second diameter by a first percentage, and the second diameter is greater than the third diameter by a second percentage. 12 . The inertial measurement unit of claim 11 , wherein the first percentage is 30% to 55%, and the second percentage is 30% to 55%. 13 . The inertial measurement unit of claim 11 , wherein the second diameter is 4 to 25 μm. The inertial measurement unit of claim 11 , wherein the first height is substantially equal to the first diameter.

15. The inertial measurement unit of claim 10, wherein the drain hole includes a seal at the upper surface and having a sealing surface having a controlled surface roughness characteristic of a reduced surface roughness height. 16 . The inertial measurement device of claim 1 , wherein the first height is 15 to 50 μm.

17. An inertial measurement device for controlling surface roughness during laser sealing, the device comprising: A membrane having an upper surface and defining a drain hole extending downward from the upper surface, the drain hole having a first height and a first cross-section perpendicular to the first height, the drain hole having a second height and a second cross-section perpendicular to the second height, the first height being disposed above the second height, the first cross-section being larger than the second cross-section so as to form a shoulder portion between the first cross-section and the second cross-section, the shoulder portion, the first cross-section, and the first height together creating a volume configured to control surface roughness during laser sealing of the drain hole.

18. The inertial measurement unit of claim 17, wherein the first cross-section and the second cross-section are similar. 19 . The inertial measurement device of claim 18 , wherein both the first cross section and the second cross section are circular, elliptical, or polygonal in shape.

20. The inertial measurement unit of claim 17, wherein both the first cross-section and the second cross-section are circular in shape.

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