JP3128812B2 - Wet etching equipment - Google Patents

Description

The present invention relates to a wet etching apparatus for etching a polysilicon layer or an aluminum layer formed on a wafer with a mixed solution of hydrofluoric acid, phosphoric acid, and nitric acid.

[Conventional technology]

FIG. 3 is a block diagram schematically showing an example of a conventional wet etching apparatus. Conventionally, this type of wet etching apparatus includes, for example, as shown in FIG. 3, a treatment tank 1 for treating a wafer with an etching solution, a washing tank 11 for washing the treated wafer with water, and an etching solution for the treatment tank 1. Storage tank 8 for supplying the etching solution, a chemical supply tank for replenishing the etching solution into the chemical storage tank 8, a spray nozzle 2 in the processing tank 1 for spraying the etching solution onto the wafer, And an etching point sensor 12 for detecting the degree of etching.

The operation of the wet etching apparatus is as follows. First, a semiconductor substrate to be etched is put into a processing tank 1, and an etching solution is sprayed on the semiconductor substrate by a spray nozzle 2,
Start etching. Next, the endpoint sensor 12
Detects the degree of etching, and terminates the etching.
Next, the semiconductor substrate is transferred to the washing tank 11 and washed. Here, the chemical supplied from the spray nozzle 2 is supplied to the treatment tank 1.
It is stored in the chemical liquid storage tank 8 from inside through a pipe. The chemical in the chemical storage tank 8 is again supplied to the spray nozzle 2 via the pipe. When the amount of the chemical solution as the etchant decreases or the properties of the chemical solution deteriorate, the lower limit sensor 3 reacts, and the chemical solution is automatically replenished from the chemical solution supply tank 6 to the chemical solution storage tank 8, Is filled and the upper limit sensor 4 reacts, the supply of the chemical solution is stopped.

On the other hand, the criteria for the deterioration of the chemical solution were determined by the following items.

1. When the etching time is out of specification. 2. After etching, observe the surface of the semiconductor substrate, which is the workpiece, with a microscope. When one of the criteria was met, the drain valve 5 was opened, and the used chemical in the chemical storage tank 8 was drained.

[Problems to be solved by the invention]

However, in the above-described conventional wet etching apparatus, it is only necessary to observe the degree of etching with an end point sensor and determine whether or not the etching is completed.
Because we do not know the etching rate quantitatively,
It is difficult to accurately determine whether a chemical solution as an etchant has deteriorated. For this reason, there is a disadvantage that the etching time is not constant and the etching surface is not uniform.

An object of the present invention is to provide a wet etching apparatus that eliminates such a drawback.

[Means for solving the problem]

The features of the present invention include a processing tank for storing a semiconductor substrate having a film to be etched formed thereon, a spray nozzle for spraying an etching solution on the semiconductor substrate, and an endpoint sensor for detecting completion of etching of the semiconductor substrate. A chemical storage tank for storing the etching chemical,
In a wet etching apparatus having a drain valve for discharging the etching chemical in the chemical storage tank and a liquid supply valve provided in a pipe connecting the chemical storage tank and the chemical supply tank, the same film as the film is provided. Is formed, a resistance measuring device for measuring a change in the resistance value of the resistor when the semiconductor substrate and the resistor are etched, and the drain valve and the supply valve are supplied by a signal from the resistance measuring device. And a valve controller for controlling opening and closing of the liquid valve.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a wet etching apparatus showing one embodiment of the present invention. As shown in FIG. 1, the wet etching apparatus includes a resistor 9 formed of the same material as a layer of a semiconductor substrate to be etched, a resistance measuring device 10 for measuring a resistance value of the resistor 9 at any time, Resistance measuring instrument
That is, a valve control unit 13 that controls the opening and closing of the drain valve 5a and the supply valve 7a by the signal of 10 is provided. Otherwise, it is the same as the conventional one.

The resistor 9 is a substrate of the same quality as the semiconductor substrate to be etched, and a film of the same quality as the film to be etched is formed on the substrate surface. For example, when etching a polysilicon layer formed on a semiconductor substrate, a thick polysilicon layer is formed on the substrate of the resistor 9. When the aluminum layer is etched, an aluminum layer of the same material is formed. Then, a chemical solution is sprayed from the spray nozzle 2 on the resistor 9, and the formation layer of the resistor 9 is etched simultaneously with the layer to be etched of the object to be etched, and the rate of change of the resistance value of the resistor 9 is measured. Monitoring the etching rate.

FIG. 2 is a flowchart for explaining the operation of the wet etching apparatus of FIG. Next, the operation of the wet etching apparatus will be described. First, a semiconductor substrate on which a polysilicon layer as an object to be etched is formed is housed in the processing bath 1. At the same time, the resistor 9 having a thick polysilicon layer formed on the semiconductor substrate is removed. Next, operation A
Then, etching is started. Next, in an operation B, the resistance value of the resistor 9 is continuously measured by a resistance measurement odd 10 and is calculated by a CPU (not shown) to calculate an etching rate. Next, in the determination operation C, the calculated etching speed is compared with an etching reference speed set separately. If the etching rate is higher than the reference, that is, NO, operation D connects the etching. Next, in a determination operation E, the degree of etching of the end point sensor is detected. If YES here, the etching is terminated.

If the determination operation C is YES and the operation is F, in operation F, the drain valve 5a is opened by the valve
Is discharged, the drain valve 5a is closed again, the supply valve is opened, and a new chemical solution is replaced. Next, the etching is started again in operation A.

Further, if the determination operation E is NO, the operation B is performed and the etching is continued. As described above, in the present wet etching apparatus, the etching rate is monitored, and the etching chemical is automatically changed according to the change.

〔The invention's effect〕

As described above, the present invention provides a resistor in which a film of the same material as the film material of a workpiece to be etched is formed in a processing tank, and the resistor film when the resistor is etched. By measuring the resistance and monitoring the etching rate, the effectiveness of the etching solution can be constantly measured, so that a wet etching apparatus capable of performing uniform etching in a shorter time can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a wet etching apparatus showing one embodiment of the present invention, FIG. 2 is a flowchart for explaining the wet operation of FIG. 1, and FIG. It is a block diagram. 1 ... Treatment tank, 2 ... Spray nozzle, 3 ... Capacity lower limit sensor, 4 ... Capacity upper limit sensor, 5,5a ... Drain valve,
6 ... Chemical supply tank, 7,7a ... Chemical supply tank, 8 ...
… Chemical storage tank, 9… resistor, 10… resistance measuring instrument,
11: Rinse tank, 12: Endpoint sensor, 13: Valve control unit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/306 H01L 21/3063 H01L 21/66

Claims (1)

(57) [Claims] 1. A processing tank for storing a semiconductor substrate having a film to be etched formed thereon, a spray nozzle for spraying an etching solution on the semiconductor substrate, an end point sensor for detecting completion of etching of the semiconductor substrate,
Wet having a chemical storage tank for storing the etching chemical, a drain valve for discharging the etching chemical in the chemical storage tank, and a supply valve provided on a pipe connecting the chemical storage tank and the chemical supply tank. In an etching apparatus, a resistor on which a film having the same quality as the film is formed, a resistance measuring device for measuring a change in a resistance value of the resistor when the semiconductor substrate and the resistor are etched, and the resistance measuring device And a valve controller for controlling the opening and closing of the drain valve and the supply valve in response to the signal of (1).