JPS6151928A - Etching device for semiconductor thin film - Google Patents

Abstract

PURPOSE:To improve the LSI yield by reducing defects of the LSI under inhibition of the increase in throughput and in the amount of microparticles deposited on a wafer by a method wherein the processing solution is rapidly exhausted, filtered, circulated, and supplied after 1-batch processing. CONSTITUTION:The used solution of a required acid such as hydrofluoric acid passes from a supply bath 11 through a pressure pump 12 and is then supplied by split into etching baths 18 and 19 by operating valves 14 and 15 after passage through a filter 13. After etching finishing by processing the wafer in the bath 18, the solution of the bath 18 is rapidly exhausted to a reserve tank 22 through a valve 20. Thereafter, the solution is once accumulated in a storing bath 27 through a pump 23, filters 24 and 25, and a pump 26, and returned to the bath 18 by opening a valve 16 by utilizing a fall. During this operation, a next batch is etched in the bath 19, and the solution is rapidly exhausted to the reserve tank 22 by opening a valve 21 after processing, and is then returned to the bath 19 by opening a valve 17 after recirculation by the same operation. In order to actually increase the number of processing, the same processings should be performed repeatedly in succession with a majority of processing baths.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an apparatus for wet etching a nitrogen film (eg, oxide film, nitride film, polysilicon) formed on a semiconductor substrate.

(Prior art) Conventional CVD film (Chemical, Vapor, De
In wet etching baths for thermal oxide films or thermal oxide films, the etching solution is mainly acids (hydrofluoric acid, phosphoric acid, etc.).

Each time a certain number of treatments is exceeded, the treatment solution is replaced or the overflow is recycled and reused. This is normal usage.

The purpose of this method is to save costs on chemical solutions and increase throughput per unit time. The frequency of replacing the etching solution is once every 1 to 2 days. However, with conventional etching methods, etched films (polysil, nitride, etc.
The drawback is that particles (residues of oxide film) and associated foreign matter float in the etching solution, and as the amount of processing increases, the number of floating particles increases, and the particles (residues) re-adhere to the semiconductor substrate after etching has been completed. was there. These particles cause pattern defects, abnormal protrusions, abnormal diffusion, etc. of the LSI, resulting in a decrease in yield. Particularly in the etching process before the growth of a gate oxide film, which is important for ICs, particle adhesion causes a drop in breakdown voltage and becomes an important problem.

(Object of the Invention) An object of the present invention is to provide an etching apparatus in which less foreign particles are attached during a wet etching process.

(Configuration of the Invention) The configuration of the present invention includes a plurality of processing tanks, and a machine g for rapidly discharging, filtering, and circulating the processing liquid and re-supplying it to the processing tanks. In addition, the above operation is repeated 9 times in a plurality of processing tanks in sequence. Furthermore, the new liquid to be supplied to the treatment tank is prepared in a separate system.

(Function) The etching apparatus of the present invention etches CV formed on a semiconductor substrate.
This is intended to solve the problem that when etching a D film or a thermal oxide film, residues (particles) of the CVD film that have once separated from the substrate float in the etching solution and re-adhere to the semiconductor substrate. This is intended to minimize the number of particles that re-adhere to the semiconductor substrate by rapidly discharging the liquid that has been subjected to bathing treatment.

(Effects of the Invention) The effects of the present invention are that particles re-adhering to the semiconductor substrate can be suppressed because the liquid is drained and filtered every time one patch is processed.
Pattern defects, abnormal protrusions, abnormal diffusion, etc. of I can be reduced, and an improvement in LSI yield can be achieved.

(Example) First, a conventional etching apparatus will be described with reference to a schematic diagram.

1 in FIG. 1 is a supply tank for the processing solution used, and by operating the pulp 2, the etching solution is poured into the processing tank 3. The semiconductor substrate is placed in a wafer carrier and etched using a punch process. The liquid 3 in this processing tank overflows and is passed through 4, filtered by a pressure pump 5, passed through a constant temperature tank 6), passed through a filter 7, and returned to the processing tank 3 via a line 8.

In this conventional example, since only an overflow amount of the processing liquid is flowed, particles floating in the processing tank 3 adhere to the surface of the semiconductor substrate.

For example, 25 pieces of 4-inch substrates were tied together and processed in 1O batch, washed with water, dried, and examined with a laser dust detector. The total number of particles larger than 0.5 μm was 103 to 10.
``I used a 74-inch wafer.

Next, examples of the present invention will be described.

In Fig. 2, the required acid (for example, 7-acid) is supplied to the filter 1 through a pressure pump 12.
Etching tank 18 with pulp operation of 14.15 through 3
, 19. Now, after the wafer is processed in the tank 18 and etching is completed, the liquid in the tank 18 is quickly drained into the reserve tank 22 through the pulp 20. After that, the pump 23, filter 24° 25, and pump 26 are passed through, and the pulp is temporarily stored in the storage tank 27. Next, the pulp 16 is opened using the head and the 4W18
Return to During this operation, the next batch is etched in tank 19, and after treatment pulp 21 is opened to quickly drain into reserve tank 22. Afterwards, the same operation is performed to recirculate the pulp 17 and return it to the tank 19. In fact, to increase the number of treatments, it is sufficient to use a plurality of treatment tanks or more and repeatedly perform the next treatment.

After processing 10 patches (10 carriers) of 25 4-inch substrates in the etching bath of the present invention as described above, washing with water and drying, a laser dust inspection device detects particles of 0.5 μm attached to the wafers. When we investigated the number of particles above, it was 10 to 1o2? This is ~1 order of magnitude lower than the value obtained with a 74-inch wafer and conventional equipment.

Compared to the conventional device, the effect of the device of the present invention is L.
A ~10% improvement in SI yield was achieved.

(Summary of Description of the Invention) The present invention provides a novel etching apparatus for CVD thin films or thermal oxide films formed on semiconductor substrates.

The key point is to rapidly drain, filter, circulate, and supply the processing solution after one batch of processing.
This can reduce defects in SI and contribute to improving the yield of LSI.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional etching apparatus, in which 1 is a supply tank, 2 is a pulp, 3 is a processing tank, and 4 is a schematic diagram of a conventional etching apparatus.
is an overflow line, 5 is a pressure pump, 6 is a constant temperature bath,
7 is a filter, and 8 is a return line. FIG. 2 is a schematic diagram showing an etching apparatus according to an embodiment of the present invention, 11 is a supply tank, 12 is a pump, 13 is a filter, 14, 15, 16.17 is pulp, 18.19
is a processing tank, 20.21 is pulp, 22 is a liquid storage tank, 2
3 is the pump, 24°25 is the filter, 26 is the pump,
27 is a liquid storage tank. λL 1゜Representative Patent Attorney Uchihara Yoj...i/
／゛＼、−′　゛　　　　　　　

Claims (1)

[Claims] In an apparatus having a plurality of etching tanks in a wet etching process of a thin film formed on a semiconductor substrate, immediately after etching is completed, the etching solution is rapidly drained from the tank, filtered, and circulated and returned to the etching tank. An etching device characterized in that etching is performed by alternately switching the baths.