阅读说明：本技术 监测具有悬空结构的传感器释放状态的方法 (Method for monitoring release state of sensor with suspension structure ) 是由 刘超 傅剑宇 侯影 刘瑞文 陈大鹏 于 2019-11-29 设计创作，主要内容包括：本发明提供一种监测具有悬空结构的传感器释放状态的方法,包括以下步骤：根据热学参数计算公式获得器件的理论热学参数值；采用电学等效测试法,测得器件的实际热学参数值；对比器件的理论热学参数值和实际热学参数值,并根据热学参数与释放工艺状态的映射模型,判断是否存在释放工艺缺陷以及缺陷类型。本发明提出的检测方法,不用破坏器件结构,且测试效率快、准确度高且适用于自动化测试。(The invention provides a method for monitoring the release state of a sensor with a suspension structure, which comprises the following steps: obtaining theoretical thermal parameter values of the device according to a thermal parameter calculation formula; measuring the actual thermal parameter value of the device by adopting an electrical equivalent test method; and comparing the theoretical thermal parameter value with the actual thermal parameter value of the device, and judging whether the release process defect and the defect type exist according to the mapping model of the thermal parameter and the release process state. The detection method provided by the invention does not damage the device structure, has high test efficiency and high accuracy, and is suitable for automatic test.)

1. A method of monitoring a release state of a sensor having a suspended structure, comprising the steps of:

obtaining theoretical thermal parameter values of the device according to a thermal parameter calculation formula;

measuring the actual thermal parameter value of the device by adopting an electrical equivalent test method;

and comparing the theoretical thermal parameter value with the actual thermal parameter value of the device, and judging whether the release process defect and the defect type exist according to the mapping model of the thermal parameter and the release process state.

2. The method of monitoring a released state of a sensor having a suspended structure according to claim 1, wherein:

the device thermal parameters include: heat capacity, solid thermal conductance, and gas thermal conductance rate of change.

3. The method of monitoring a released state of a sensor having a suspended structure according to claim 2, wherein:

comparing theoretical thermal parameter values with actual thermal parameter values of the device, and according to a mapping model of the thermal parameters and the release process state, if the heat capacity, the solid thermal conductivity and the gas thermal conductivity change rate are not changed, determining that the device is a normal device; if the heat capacity, the solid thermal conductivity and the gas thermal conductivity change rate are large, the device is an under-release device; if the heat capacity is larger and the change rates of the solid thermal conductivity and the gas thermal conductivity are smaller, the device is an over-release device.

4. A method of monitoring a released state of a sensor having a suspended structure according to claim 3, wherein:

the heat capacity H is calculated by the formula:

wherein v is_i,、ρ_i,、γ_iRespectively representing the volume, density and specific heat capacity of the ith layer material of the suspension unit;

solid thermal conductance G_canThe calculation formula of (2) is as follows:

wherein N is the number of cantilever beams, k_bIs the thermal conductivity of the cantilever beam, W_b、d_bAnd L_bThe width, thickness and length of the cantilever beam are respectively;

the gas conductance change rate gamma is the gas conductance G_gasThe rate of change with gas pressure P is expressed as:

wherein k is_air,0For gas thermal conductivity at room temperature and atmospheric pressure, d_λIs the gap between the suspended unit and the substrate, A_sIs the area of the floating unit, T is floatingThe temperature of the cell.

5. A method of monitoring a released state of a sensor having a suspended structure according to claim 3, wherein:

the electrical equivalent test method of the thermal parameters is as follows:

arranging a thermosensitive element in a suspension unit of the device, connecting the thermosensitive element of the device with a fixed resistor R in series, and supplying power by a voltage source; controlling a voltage source to generate a square wave voltage, wherein the high level is U, and the low level is 0; the heat sensitive element obtains a Joule heating power P_sh(ii) a Measuring the thermal power through voltage and current on the thermosensitive element; under the action of the thermal power, the suspension unit is heated, the resistance of the thermosensitive element is changed at the moment, so that the voltage at two ends of the thermosensitive element is changed, the variable quantity is delta V, and according to a thermal balance equation, the relational expression of the voltage variable quantity of the thermosensitive element along with time is as follows:

α is the voltage temperature coefficient of the thermosensitive element, and tau is the thermal response time of the device;

when the heating time is long enough, the device reaches a thermal equilibrium state, and the total thermal conductance is:

gas thermal conductance G under vacuum_gasIs 0, so that the solid thermal conductance G of the device can be obtained under the vacuum state_can(ii) a Solid state thermal conductance G under non-vacuum state_canSame as in the vacuum state;

changing the gas pressure to obtain the gas thermal conductivity change rate gamma of the device under the non-vacuum state;

according to H ═ τ × (G)_can+G_gas) And using the obtained measurement value to obtain the heat capacity of the device.

Technical Field

The invention belongs to the field of microelectronic reliability analysis, and particularly relates to a method for monitoring a release state of a sensor with a suspension structure, which can be used for process monitoring of a release process state of the sensor.

Background

The release process is a key process for manufacturing suspended structures, and comprises bulk silicon release and surface sacrificial layer release. Due to non-ideal factors in the process, under-release defects and over-release defects may occur in the suspended structure, so that the performance parameters of the device are abnormal or the function of the device is invalid. Currently, since such defects occur inside the device structure, release process defect detection is mostly aided by optical devices, such as: optical microscopes, scanning electron microscopes, atomic force microscopes, and the like. The detection mode is destructive, and the low testing efficiency is not beneficial to large-scale automatic testing. Therefore, the research on the rapid and nondestructive detection method of the release process has important significance.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a method for monitoring the release state of a sensor with a suspended structure. The technical scheme adopted by the invention is as follows:

a method of monitoring a release state of a sensor having a suspended structure, comprising the steps of:

obtaining theoretical thermal parameter values of the device according to a thermal parameter calculation formula;

measuring the actual thermal parameter value of the device by adopting an electrical equivalent test method;

and comparing the theoretical thermal parameter value with the actual thermal parameter value of the device, and judging whether the release process defect and the defect type exist according to the mapping model of the thermal parameter and the release process state.

Further, the device thermal parameters include: heat capacity, solid thermal conductance, and gas thermal conductance rate of change.

Furthermore, comparing theoretical thermal parameter values with actual thermal parameter values of the device, and according to a mapping model of the thermal parameters and the release process state, if the heat capacity, the solid thermal conductivity and the gas thermal conductivity change rate are not changed, the device is a normal device; if the heat capacity, the solid thermal conductivity and the gas thermal conductivity change rate are large, the device is an under-release device; if the heat capacity is larger and the change rates of the solid thermal conductivity and the gas thermal conductivity are smaller, the device is an over-release device.

The invention has the advantages that:

1) compared with the prior art, the method provided by the invention does not damage the device structure, has high test efficiency and high accuracy, and is suitable for automatic test.

2) The method provided by the invention can distinguish and identify the release state of the device, can acquire the thermal parameters of the device and provides guidance for optimizing the performance of the device and improving the process.

3) The proposed method may provide a process control Patterning (PCM) solution for process monitoring of the release process.

Drawings

FIG. 1a is a schematic side sectional view of a thermal infrared sensor device according to an embodiment of the present invention.

Fig. 1b is a schematic top view of a thermal infrared sensor device according to an embodiment of the present invention.

FIG. 2 is a flow chart of the analysis method of the present invention.

Detailed Description

The invention is further illustrated by the following specific figures and examples.

The embodiment of the invention provides a method for monitoring the release state of a sensor with a suspension structure, which takes a thermal infrared sensor device with the suspension structure as an example, and in other embodiments, the analysis method can also be applied to other devices with the suspension structure;

as shown in fig. 1a and 1b, the thermal infrared sensor device includes a substrate 1, a frame 2, a release cavity 3 and a suspension structure; the frame 2 is connected on the substrate 1, and a release cavity 3 is arranged in the frame 2; the suspension structure comprises a suspension unit 4, a cantilever beam 5 and a thermosensitive element 6; the suspension units 4 are erected on the frame 2 through cantilever beams 5 (two in this example) and are positioned above the release cavities 3; a thermosensitive element 6 is arranged in the suspension unit 4; if the device has a thermosensitive element in the normal function, the thermosensitive element 6 just meets the requirements of the device; if the device does not contain a thermosensitive element in the normal function, the thermosensitive element can be added in the suspension unit 4 to meet the test requirement;

a method of monitoring a release state of a sensor having a suspended structure, comprising the steps of:

obtaining theoretical thermal parameter values of the device according to a thermal parameter calculation formula;

measuring the actual thermal parameter value of the device by adopting an electrical equivalent test method;

and comparing the theoretical thermal parameter value with the actual thermal parameter value of the device, and judging whether the release process defect and the defect type exist according to the mapping model of the thermal parameter and the release process state.

The device thermal parameters include: heat capacity, solid thermal conductivity, and gas thermal conductivity change rate;

the heat capacity H is calculated by the formula:

wherein v is_i,、ρ_i,、γ_iRespectively representing the volume, density and specific heat capacity of the ith layer material of the suspension unit; the suspension unit 4 may comprise three or four layers of material in some embodiments;

solid thermal conductance G_canThe calculation formula of (2) is as follows:

wherein N is the number of cantilever beams, k_bIs the thermal conductivity of the cantilever beam, W_b、d_bAnd L_bThe width, thickness and length of the cantilever beam are respectively;

the gas conductance change rate gamma is the gas conductance G_gasThe rate of change with gas pressure P is expressed as:

wherein k is_air,0For gas thermal conductivity at room temperature and atmospheric pressure, d_λIs the gap between the suspended unit and the substrate, A_sIs the area of the suspended unit, and T is the temperature of the suspended unit;

the electrical equivalent test method of the thermal parameters is as follows:

connecting a thermosensitive element of the device with a fixed resistor R in series, and supplying power by a voltage source; controlling a voltage source to generate a square wave voltage, wherein the high level is U, and the low level is 0; the heat sensitive element obtains a Joule heating power P_sh(ii) a The thermal power can be measured through voltage and current on the thermosensitive element; under the action of the thermal power, the suspension unit is heated, the resistance of the thermosensitive element is changed at the moment, so that the voltage at two ends of the thermosensitive element is changed, the variable quantity is delta V, and according to a thermal balance equation, the relational expression of the voltage variable quantity of the thermosensitive element along with time is as follows:

α is the voltage temperature coefficient of the thermosensitive element, and tau is the thermal response time of the device;

according to the formula 7, the thermal response time τ of the device is the time required for the voltage variation of the thermosensitive element to change from 0 to 63.2% of the maximum value;

when the heating time is long enough, the device reaches a thermal equilibrium state, and the total thermal conductance is:

gas thermal conductance G under vacuum_gasIs 0, and thus can be in a vacuum stateSolid thermal conductance G of lower gain device_can(ii) a Solid state thermal conductance G under non-vacuum state_canSame as in the vacuum state;

changing the gas pressure to obtain the gas thermal conductivity change rate gamma of the device under the non-vacuum state;

according to H ═ τ × (G)_can+G_gas) And obtaining the heat capacity of the device by using the obtained measured value;

the release process state comprises normal release, under release and over release;

the mapping model of thermal parameters to release process conditions can be represented by a table:

	heat capacity	Solid heat conduction	Rate of change of gas thermal conductance
				Normal device	Is not changed	Is not changed	Is not changed
Under-release device	Greater and greater	Greater and greater	Greater and greater
				Over-release device	Greater and greater	Is slightly small	Is slightly small

Comparing theoretical thermal parameter values with actual thermal parameter values of the device, and according to a mapping model of the thermal parameters and the release process state, if the heat capacity, the solid thermal conductivity and the gas thermal conductivity change rate are not changed, determining that the device is a normal device; if the heat capacity, the solid thermal conductivity and the gas thermal conductivity change rate are large, the device is an under-release device; if the heat capacity is larger and the change rates of the solid thermal conductivity and the gas thermal conductivity are smaller, the device is an over-release device.

Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.