JP2003106884A - Airflow sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an airflow sensor that can accurately measure the flow velocity, flow rate, direction, etc., of a fluid flowing along the surface of a substrate. SOLUTION: A plurality of flow sensors 10 is embedded in the surface of the substrate 7 so as to detect the flow velocity of a gas 4 flowing through each section on the surface of the substrate 7 and the temperature distribution of the substrate 7 by means of the sensors 10. Each flow sensor 10 is provided with a heating element, two temperature sensors respectively provided on the upstream and downstream sides of the heating element, and an ambient temperature detecting means.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an airflow sensor suitable for use in a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art In the semiconductor market, with the recent advances in fine processing technology (micromachine technology) and the increase in the diameter of silicon wafers, pattern miniaturization and cost reduction are progressing more and more. Currently, large diameter 300 mm
The mass production of semiconductor ICs having a pattern width of 0.13 μm on the wafer is rapidly progressing. In this case, for example, when a pattern having a pattern width of 0.13 μm is formed on a silicon wafer having a diameter of 300 mm and a thermal expansion coefficient of 2.6 × 10 ⁻⁶ / ° C., the temperature difference between the both ends of the peripheral edge of the silicon wafer is 0. Assuming that 0.011 ° C. (10 m ° C.) occurs, the pattern width is ± 0.0078 μm (= 300 × 10 ⁻³ × 2.6 × 10 ⁻⁶ × 0.0
1) Expand and contract. In other words, if there is a temperature difference of ± 10 m ° C,
The pattern width varies by 0.13 μm ± 6% (= 0.0078 / 0.13), which causes a decrease in yield. For this reason,
Larger diameter silicon wafers in semiconductor manufacturing equipment,
In order to miniaturize the pattern, it is necessary to measure the temperature of the wafer surface and control it with high accuracy.

Therefore, in order to measure the surface temperature of the silicon wafer, for example, a temperature sensor device disclosed in Japanese Patent Laid-Open No. 2000-241257 is used. In this temperature sensor device, a large number of resistor temperature sensors are provided scattered on a substrate, and conductive lines of each resistor temperature sensor are formed in close contact with the substrate surface together with external lead wire connecting terminals. At the time of measurement, the resistance value of the resistor temperature sensor at a predetermined temperature is measured in advance, and the resistance value compared with the resistance value data in the temperature measurement is converted into temperature and displayed.

[0004]

However, the above-described conventional temperature sensor device merely measures the temperature at each portion of the substrate surface, and the wafer processing fluid (air, nitrogen, etc.) flowing along the substrate surface is measured. ) No consideration was given to its own flow velocity, flow rate, flow direction, etc., and there was a problem in terms of reliability of temperature control and reliability of wafer processing. That is, since the temperature distribution of the substrate slightly changes depending on the temperature of the fluid flowing along the surface of the substrate, especially the flow velocity, the correlation between the temperature distribution of the substrate surface and the flow velocity of the fluid is investigated, and the temperature distribution of the substrate surface is uniform. It is necessary to control the fluid so that In particular, the larger the surface area of the substrate, the more difficult it is for the fluid to flow uniformly, so that the flow rate of the fluid changes, the direction of flow changes, or almost no fluid flows at each part of the substrate surface. You can do it. As a result, the whole wafer cannot be uniformly and accurately processed, and the yield is reduced. Therefore, there is a demand for the development of an airflow sensor capable of accurately measuring the flow velocity, flow rate, and flow direction of the fluid in each part of the substrate.

The present invention has been made to meet the above-mentioned problems and demands of the related art, and its purpose is to:
An object of the present invention is to provide an airflow sensor capable of accurately measuring the flow velocity, temperature, direction, etc. of a fluid flowing along the surface of a substrate.

[0006]

In order to achieve the above-mentioned object, the present invention comprises a plurality of flow sensors embedded in the surface of a substrate, and these flow sensors enable the flow of fluid flowing through each part of the surface of the substrate. The flow velocity and the temperature of the substrate are detected. In the present invention, the flow velocity of the fluid flowing through each part of the surface of the substrate and the temperature of the substrate are measured. Since the flow sensor is embedded in the substrate, it does not disturb the flow of fluid.

A second invention is the same as the first invention,
The substrate is a silicon wafer, the flow sensor is provided with a heating element, two temperature sensors arranged on the upstream side and the downstream side with the heating element sandwiched between them, and an ambient temperature detecting means. The flow velocity and the direction of the flow are detected. In the present invention, when a temperature difference occurs between the two temperature sensors, the flow velocity of the fluid and the flow direction of the fluid can be detected by detecting the voltage difference or the resistance value difference. Regarding the flow direction of the fluid, when the temperature sensors are arranged on the upstream side and the downstream side, the temperature of the upstream temperature sensor is low and the temperature of the downstream temperature sensor is high. Therefore, the direction of fluid flow can be detected.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. FIG. 1 is a sectional view of an airflow sensor according to the present invention, FIG. 2 is a plan view of the airflow sensor, and FIG.
(A), (b) is the top view and front view of a flow sensor,
FIG. 4 is a diagram showing a constant temperature difference circuit of the flow sensor, and FIG. 5 is a diagram showing a sensor output circuit. In these figures, reference numeral 1 denotes a heat treatment device for heat-treating a silicon wafer, 2 denotes a wafer mounting table, 3 denotes a wafer mounting table 2
Together with this, it is a top cover that forms the flow path 5 for the gas 4.

Reference numeral 6 denotes an air flow sensor for the wafer, which measures the flow velocity, temperature, flow rate, flow direction of the gas 4 flowing in the flow path 5, and ambient temperature (substrate temperature). Substrate 7 set on the wafer mounting table 2
And a total of 18 thermal type flow sensors 10 embedded in the upper surface of the substrate 7 and a controller 11. The controller 11 and each of the flow sensors 10 are electrically connected by a terminal drawing substrate 12. There is.

The substrate 7 is made of a silicon wafer having substantially the same size as the silicon wafer to be heat-treated by the heat treatment apparatus 1, and two flow sensors 10 are provided at the center of the upper surface.
However, 16 flow sensors 10 are embedded in the peripheral portion of the upper surface at equal intervals (22.5 °) in the circumferential direction. Board 7
A concave portion 19 is previously formed by etching, laser processing, or the like in a portion of the surface where the flow sensor 10 is embedded.

As shown in FIG. 3, the flow sensor 10 is composed of a substrate 13, a flow velocity detecting means 15 and an ambient temperature detecting means 16 formed on the surface of the substrate 13 via an electric insulating film 14. .

The substrate 13 is formed in a thin plate shape and is bonded to the recess 19 of the substrate 7 with an adhesive or the like.
As a material of the substrate 13, a material having a lower thermal conductivity than silicon and having high heat resistance, corrosion resistance and rigidity is used. In this case, in the present embodiment, the plate thickness is 1 to 3.
An example in which the substrate 13 is formed of a thin plate of stainless steel (in particular, SUS316L) having a size of about mm is shown, but a substrate made of an insulating material such as sapphire or ceramic may be used.

The surface of the substrate 13 is mirror-polished and the electrical insulating film 14 is formed over the entire surface. Further, the flow velocity detecting means 1 is provided on the surface of the electric insulating film 14.
5. The ambient temperature detecting means 16 includes a plurality of electrode pads 1
7 and the metal thin film 18 for wiring are formed by a well-known photolithography technique and etching technique. For example, a material such as platinum is vapor-deposited on the surface of the electric insulating film 14 and is formed by etching into a predetermined pattern, and the flow velocity detecting means 15 and the ambient temperature detecting means 16 are connected to the electrode pad 17 via the wiring metal thin film 18. Are electrically connected to each other. Further, each electrode pad 17 is connected to an electric circuit of the terminal lead-out substrate 11. The surface of the substrate 13 is covered with an insulating protective film 20.

As the electric insulating film 14, for example, thin silicon oxide (Si) having a thickness of about several thousand angstroms is used.
It is formed of an O ₂ ) film or a silicon nitride film. The silicon oxide film is formed by, for example, sputtering, CV
It can be formed by applying a solvent containing D or silicon oxide and heating it to a predetermined temperature to melt and solidify the silicon oxide. The silicon nitride film can be formed by sputtering or CVD.

The flow velocity detecting means 15 and the ambient temperature detecting means 16 will be described in more detail with reference to FIG. Flow velocity detection means 1
5 is one heating element 21 and two temperature sensors 22A, 2
2B and constitutes an indirectly heated flow velocity detecting means. The heating element 21 is formed substantially in the center of the substrate 13.
The two temperature sensors 22A and 22B are formed so as to be respectively located on the upstream side and the downstream side in the flow direction of the gas 4 with the heating element 21 interposed therebetween. The ambient temperature detecting means 16 is used to compensate for a change in the ambient temperature, that is, the temperature of the fluid 5, and is formed on the upstream side of the upstream temperature sensor 22A near the outer periphery of the substrate 13. Has been done. The pattern width of the heating element 21 is 10 to 50 μm,
Temperature sensors 22A, 22B and ambient temperature detecting means 16
The pattern width is preferably about 5 to 10 μm.

In FIG. 4, the ambient temperature detecting means 16, the heating element 21 and the three fixed resistors R1, R2 and R3 form a bridge circuit, and this and an operational amplifier (OP1) form a constant temperature difference circuit of the flow sensor 10. Is forming. OP1
Uses the bridge circuit, the resistor R1 and the midpoint voltage of the heating element 21 as the inverting input, and the midpoint voltage of the resistors R2 and R3 as the non-inverting input. The output of this OP1 is resistor R
1 and R2 are commonly connected to one end. Resistors R1 and R
The resistance values of 2 and R3 are set so that the temperature of the heating element 21 is always higher than the ambient temperature detecting means 16 by a constant temperature.

In FIG. 5, two temperature sensors 22A,
22B and two fixed resistors R4 and R5 form a bridge circuit, and this and the operational amplifier (OP2) form a flow sensor 1.
0 sensor output circuit is formed.

In the wafer air flow sensor 6 having such a flow sensor 10, the heating element 21 is heated to a certain higher temperature than the ambient temperature by energizing the bridge circuit of the constant temperature difference circuit shown in FIG. When the gas 4 is supplied to the flow path 5 in this state, the gas 4 flows toward the center along the surface of the substrate 7 and is guided from the discharge port 8 to above the upper surface cover 3. When the gas 4 flows along the surface of the substrate 7, the substrate 13 of the flow sensor 10 is deprived of heat by the gas 4 in proportion to its flow rate. In addition, the heating element 21 is also deprived of heat, so that the resistance value is lowered. Therefore, the equilibrium state of the bridge circuit is lost, but since a voltage corresponding to the voltage generated between the inverting input and the non-inverting input is applied to the bridge circuit by OP1, heat is generated so as to compensate for the heat taken by the gas 4. The calorific value of the body 21 increases. As a result, the resistance value of the heating element 21 increases, and the bridge circuit returns to the equilibrium state. Therefore, a voltage corresponding to the flow velocity is applied to the bridge circuit in the balanced state. The constant temperature difference circuit of FIG. 4 outputs the voltage between the terminals of the heating element 21 among the voltages applied to the bridge circuit at this time as a voltage output.

When the gas 4 takes away the heat of the heating element 21, a temperature difference is generated between the temperature sensor 22A located upstream of the heating element 21 and the temperature sensor 22B located downstream of the heating element 21, so that the sensor shown in FIG. The flow rate of the gas 4 can be detected by detecting the voltage difference or the resistance value difference by the output circuit and calculating the detection signal by the controller 11. Further, the flow direction of the gas 4 can also be detected by the temperature difference between the two temperature sensors 22A and 22B. The flow rate can be obtained by multiplying the measured flow rate by the cross-sectional area of the flow path 5.

As described above, since the wafer air flow sensor 6 detects the flow velocity, flow rate, and flow direction of the gas 4 by the flow velocity detecting means 15, and the ambient temperature detecting means 16 detects the temperature of the substrate 7, It is possible to accurately measure the flow state of the gas 4 and the temperature distribution on the substrate surface in each part on the surface of the substrate 7, and improve the temperature control of the heat treatment apparatus 1 and the reliability of wafer treatment.

In the above embodiment, the spatial temperature distribution of the gas 4 due to the heat generated from the heating element 21 is biased by the flow, and this is caused by the two temperature sensors 2.
Although the example using the indirectly heated type flow sensor 10 which detects by 2A, 22B is shown, it is not limited to this and the heating element 2 is generated by the gas 4.
It is also possible to use a self-heating type flow sensor that detects a change in electric power or a change in resistance due to the removal of heat of No. 1 and detects a flow velocity or a flow rate. The fluid is not limited to gas and may be liquid.

[0022]

As described above, according to the airflow sensor of the present invention, the flow velocity of the fluid flowing along the surface of the substrate,
The flow rate and direction, and the temperature distribution on the substrate surface can be accurately detected, which is suitable for use in a semiconductor manufacturing apparatus. Further, since the flow sensor is embedded in the surface of the substrate, it is possible to perform accurate measurement without disturbing the flow of fluid.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an air flow sensor according to the present invention.

FIG. 2 is a plan view of the airflow sensor.

3A and 3B are a plan view and a front view of a flow sensor.

FIG. 4 is a diagram showing a constant temperature difference circuit.

FIG. 5 is a diagram showing a sensor output circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat processing apparatus, 2 ... Wafer mounting table, 3 ... Top cover, 4 ... Gas, 5 ... Flow path, 6 ... Wafer air flow sensor,
7 ... Substrate, 10 ... Flow sensor, 13 ... Substrate, 14 ... Electrical insulating film, 15 ... Flow velocity detecting means, 16 ... Ambient temperature detecting means, 19 ... Recessed portion, 21 ... Heating element (heater), 22A, 2
2B ... Temperature sensor.

Claims (2)

[Claims] 1. An airflow sensor comprising a plurality of flow sensors embedded in the surface of a substrate, and detecting the flow velocity of a fluid flowing through each part of the surface of the substrate and the temperature of the substrate by these flow sensors. . 2. The airflow sensor according to claim 1, wherein the substrate is a silicon wafer, the flow sensor is a heating element, two temperature sensors arranged on the upstream side and the downstream side with the heating element interposed therebetween, and the surroundings. An air flow sensor, comprising: a temperature detecting means, wherein the flow velocity and the flow direction of the fluid are detected by the two temperature sensors.