JP3203786B2 - Method and apparatus for etching silicon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon controlled etching amount, for example, for processing a silicon diaphragm constituting a pressure detecting device with high precision.
Emissions related etching method and apparatus.

[0002]

2. Description of the Related Art For example, when manufacturing a silicon diaphragm constituting a pressure detecting device, a region of a silicon wafer where a diaphragm is to be formed is etched from one surface of the silicon wafer. A diaphragm is formed. In this case, it is necessary to control the amount of etching so that the thickness of the diaphragm is set with high accuracy.

The etching rate of a silicon wafer is calculated by measuring the amount of etching after a predetermined etching process. However, in such a method, it is necessary to take out the silicon wafer from the etching solution during the etching process and measure the etching amount, and it is not possible to know the etching rate during the etching while the silicon wafer is immersed in the etching solution.

[0004] Therefore, if it is desired to perform a desired amount of etching during the actual etching process, the dummy sample is etched before the etching operation, whereby the etching rate is calculated to determine the etching time. ing. Therefore, such means cannot control the etching amount with high accuracy, and it is difficult to reduce the instability of the etching amount.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made so that the etching amount can be calculated with high accuracy even during the etching process.
An object of the present invention is to provide a method and an apparatus for etching silicon in which the etching processing time can be reliably set in accordance with a target etching amount.

[0006] The silicon etching method according to the present invention comprises, first, the conductivity and etching efficiency of an etching solution which is an aqueous KOH solution.
The relationship with the switching speed is stored and set in advance. Second, the
Set the amount of etching for the recon. And the third
Next, the conductivity of the etching solution is measured. Next, the fourth
Then, the silicon is immersed in the etching solution. Soshi
The conductivity and etching of the stored etchant
Immersed in the etching solution based on the relationship with the speed
The silicon etching amount is calculated, and the calculated edge is calculated.
Until the amount of etching reaches the set amount of etching,
So that the silicon is immersed in the etchant
It is.

[0007] The silicon etching apparatus of the present invention
Store the etching solution, which is an aqueous KOH solution, in the etching tank.
Soak the conductivity measurement electrode in this etchant
The conductivity measuring electrode and the conductivity measuring means are connected. And act
In the calculation means, the conductivity of the etching solution, the etching rate and
Is stored and set, and measured by the conductivity measuring means.
Of silicon based on the conductivity of the etching solution
Find the amount of pitching. As a result, the
In the state where the amount of etching
This is the device that completes the silicon etching operation.

[0008]

A specific relationship exists between the concentration of the etching solution and the etching rate . Also, a specified relationship is set between the concentration of the etching solution and the conductivity of the etching solution. Therefore, the etching rate is calculated by measuring the conductivity of the etching solution by the conductivity measuring means, and the relationship between the preset etching amount and the etching time is obtained. Therefore, by determining the conductivity of the etching solution, the etching amount of silicon during etching can be determined. Thus, the amount of etching can be monitored and controlled with high accuracy.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows, for example, an etching apparatus for manufacturing a silicon diaphragm which constitutes a semiconductor pressure detecting apparatus. The etching apparatus includes an etching solution tank 11 containing an etching solution and a cleaning water tank 12 containing cleaning water.
Inside the electrode 11, the conductivity measuring electrode 13 is set by being immersed in an etching solution.

Although not shown in the figure, the electrodes 13 are appropriately configured in pairs, and the conductivity measuring electrodes are connected to a conductivity measuring device 14 so that the conductivity of the etching solution can be measured in the measuring device 14. It is always possible to measure.

The etching solution in the etching solution tank 11 is guided to the first pump / valve mechanism 16 via a pipe 151,
Further, it is guided to the nozzle mechanism 18 of the etching processing unit 17 via the pipe 152. A silicon wafer 19, which is an object to be etched, is set in the etching processing unit 17,
The etching liquid is supplied to the silicon wafer 19 from the nozzle mechanism 18. In this case, a mask is formed on the silicon wafer 19 so that the etching region is appropriately exposed.

Further, the cleaning water from the cleaning water tank 12 is also supplied to a pipe 153.
The cleaning water is guided to the first pump / valve mechanism 16 through the nozzle mechanism, and when selected by the pump / valve mechanism 16, the washing water is guided to the nozzle mechanism 18. Then, the etching solution or cleaning water stored in the etching processing unit 17 is supplied to the piping 154 by the second pump / valve mechanism 20.
Alternatively, it is led to 155 and returned to the etching liquid tank 11 or the cleaning water tank 12.

The conductivity measurement data of the etching solution measured by the conductivity measuring device 14 is supplied to a computing device 21. The arithmetic unit 21 etches, for example, a silicon wafer 19 having a thickness t as shown in FIG. 2A from one side as shown in FIG. As shown in the figure, when processing a silicon diaphragm having a thickness d, the etching amount a is obtained and set from “a = t−d”.

The first and second pump / valve mechanisms 16 and 20 are controlled by a command from the arithmetic unit 21. In the first pump / valve mechanism 16, one of the etching liquid and the cleaning water is controlled. Is selected and fed to the nozzle mechanism 18 by pressure. Further, in the second pump / valve mechanism 20, the etching liquid or cleaning water stored in the etching processing section 17 is guided to the etching liquid tank 11 or the cleaning water tank 12 according to the contents.

FIG. 3 shows the procedure of the etching process in the etching apparatus having the above-mentioned configuration. First, before the etching process, the thickness t of the silicon wafer to be processed in step 101 and the thickness d of the diaphragm are inputted. . Then, the silicon wafer 19 to which the thicknesses t and d have been input in this way is set at a predetermined position of the etching unit 17 in step 102.

At this stage, the measurement of the conductivity of the etching solution is started. In the conductivity measuring device 14 to which the conductivity measuring electrode 13 is connected, the etching rate is determined based on the conductivity of the etching solution at that time. Is calculated.

With the silicon wafer 19 set in this way, the first pump
The valve mechanism 16 is controlled, the etchant in the etchant tank 11 is pumped to the nozzle mechanism 18 via the pipes 151 and 152, and the etchant is released toward the silicon wafer 18 to start the etching in step 103. You.

In this case, the second pump / valve mechanism 20 is also controlled by a command from the arithmetic unit 21, and the etching liquid to be stored in the etching processing unit 17 is supplied to the etching liquid tank via the pipe 153. The etching liquid is guided to 11, and the etching liquid is circulated in the order of the etching liquid tank 11, the etching processing section 17, and the etching liquid tank 11.

With the etching started in this manner, the etching rate is calculated based on the conductivity of the etching solution measured by the arithmetic unit 21, and based on the calculated etching rate, the etching rate is calculated from the start of the etching to the current time. The amount of etching up to is calculated by the arithmetic unit 21.

In the arithmetic unit 21, based on the thickness t of the silicon wafer 19 and the thickness d of the diaphragm to be formed, the etching amount a (= t−
d) is set, and when it is determined that the etching amount has reached the target amount a in accordance with the etching rate calculated by the arithmetic unit 21, the arithmetic unit 21
Then, the commands given to the second pump / valve mechanisms 16 and 21 are switched, and the etching solution sent from the etching solution tank 11 to the nozzle mechanism 18 of the etching processing unit 17 is stopped. Done.

When the etching is completed in this manner, the cleaning water from the cleaning water tank 12 is supplied to the nozzle mechanism 18 via the switched first pump / valve mechanism 16, and the silicon wafer 19 in step 105 is supplied. Is performed.
In this cleaning process, the second pump / valve mechanism 20 is used.
As a result, the cleaning water stored in the etching unit 17 is returned to the cleaning water tank 12.

The arithmetic unit 21 calculates the etching rate from the conductivity of the etching solution. A method for obtaining the etching rate and the etching amount will be described.

FIG. 4A shows the dependence of the conductivity and the etching rate of the KOH aqueous solution used for the etching process for forming the silicon diaphragm on the concentration of the etching solution, and FIG. Indicates the dependence of the etching solution on the amount of dissolved silicon.

Based on the relationship shown in FIG. 4, the relationship between the conductivity of the etching solution and the etching rate is obtained.
The arithmetic unit 21 calculates the etching rate based on the measured conductivity.

As a means for obtaining the current etching amount, every predetermined unit time after the start of etching,
An average etching rate within the unit time is calculated, and an etching amount is calculated for each time unit. Then, the total etching amount up to the present time is obtained by calculating the sum of the etching amounts for each unit time up to the present time.

When a silicon wafer is etched by the etching apparatus configured as described above, the current etching rate is calculated by measuring the conductivity of the etchant as needed, and the current etching amount is determined based on the etching rate. It is required with high accuracy.
Therefore, a silicon wafer can be formed by etching with a high precision etching amount. For example, a silicon diaphragm constituting a semiconductor pressure detecting device can be manufactured under high precision thickness control, and the manufacturing process is simplified. In addition, the reliability of the product is significantly improved.

In the embodiment shown in FIG. 1, the circulation paths of the etching solution and the cleaning water are switched in accordance with the progress of the etching. However, as shown in FIG. You may make it move between the tank 21 and the washing water tank 22.

That is, the etching liquid tank 31 containing the etching liquid and the cleaning water tank 22 containing the cleaning water are arranged side by side, and the rails 33 are arranged so as to extend over the etching liquid tank 31 and the cleaning water tank 32. Is set, and the carrier 34 that is moved along the rail 33 is set. And
A large number of silicon wafers 35 to be etched are placed on the carrier 34, and the silicon wafer 35
To be transported together.

In this case, the rail on which the carrier 34 is set
33 is provided with an automatic transfer control device 36, to which a command is given from the arithmetic unit 21. The arithmetic unit 21 is supplied with the conductivity data of the etching solution measured by the conductivity measuring unit 14, and the conductivity measuring unit 14 is connected to a conductivity measuring electrode 37 set in the etching solution tank 31. .

The etching procedure in the apparatus configured as described above is the same as that described in the above embodiment. That is, based on the signal detected by the conductivity measuring electrode 37 set in the etching solution tank 31, the conductivity of the etching solution is measured by the conductivity measuring device 14, and the etching amount up to the present time is calculated by the arithmetic device 21. Is done.

When the arithmetic unit 21 determines that the etching amount determined by the predetermined diaphragm thickness d has been reached, the arithmetic unit 21 gives a command to the automatic transfer control unit 36 to set the silicon wafer 35. Career 34
The carrier 34 is moved to the cleaning water tank 32 and immersed in the cleaning water to complete the etching process.

[0032]

As described above, the silicon according to the present invention
According to the etching method and the apparatus , the etching amount is calculated with high accuracy in accordance with the progress of the silicon etching process, and the etching amount is controlled with high accuracy by a sufficiently simplified manufacturing process. Therefore, the reliability of the product is sufficiently improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an etching apparatus according to an embodiment of the present invention.

FIGS. 2A to 2C are diagrams illustrating a silicon wafer to be subjected to an etching process.

FIG. 3 is a diagram illustrating an etching procedure.

FIGS. 4A and 4B are diagrams illustrating a relationship between the conductivity of an etching solution and an etching rate.

FIG. 5 is a configuration diagram illustrating another embodiment of the present invention.

[Explanation of symbols]

11, 31… Etching liquid tank, 12, 32… Washing water tank, 13, 37…
Conductivity measuring electrode, 14: Conductivity measuring device, 17: Etching unit, 18: Nozzle mechanism, 19, 35: Silicon wafer, 21
... Computing device, 34 ... Carrier, 36 ... Automatic transfer control device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21 / 306,21 / 3063,21 / 308 C23F 1/00-1/46

Claims (3)

(57) [Claims] A first step of storing and setting in advance a relationship between the conductivity and an etching rate of an etching solution that is an aqueous solution of KOH; a second step of setting an etching amount for silicon ; and a conductivity of the etching solution. A fourth step of immersing the silicon in the etchant; a fourth step of immersing the silicon in the etchant; and a fourth step of immersing the silicon in the etchant based on a relationship between the stored conductivity and the etch rate of the etchant. Tasiri
And a fifth step of calculating an etching amount of the capacitor, wherein the silicon is immersed in an etching solution until the calculated etching amount reaches the set etching amount. Silicon etching method and apparatus. 2. The method according to claim 1, wherein in the third step, the conductivity of the etchant is measured at predetermined time intervals, and a current etching amount is calculated from a relationship between the conductivity and the etching rate. Silicon etching method. 3. An etching tank in which an etching solution which is an aqueous KOH solution is stored, a conductivity measuring electrode set by immersing the etching solution in the etching bath , and a conductivity connecting the conductivity measuring electrode. A rate measuring means, and a calculating means for storing and setting a relationship between the conductivity of the etching solution and the etching rate, and for calculating an etching amount of silicon based on the conductivity of the etching solution measured by the conductivity measuring means. provided by etching amount obtained by the calculating means, the etching apparatus of the silicon, characterized in that the etching operation of silicon is to be terminated in the state has reached a predetermined amount of etching.