JPH0465125A - Vapor etching method - Google Patents

Abstract

PURPOSE:To effectively remove a surface oxide film by etching sharply reducing the production of any particulate matter by making a sample contact with mixed gas with a 5-50 ratio of HF/H2O. CONSTITUTION:There are provided a gas mixture box 4 wherein there are oppositely connected an HF vapor supply pipe 5 extending from an HF gas bomb and an H2O vapor supply pipe 6 extending from an H2O tank, and gas introduction pipes 8, 8' for feeding mixed gas from the gas mixture box into a chamber 1. A permeability-to-gases filter 7 is disposed in the vapor gas mixture box 4 and a porous monel plate distributor 3 is disposed in the chamber 1. Etching is carried out in the state where a silicon wafer 2 as an object to be etched is placed in the chamber 1. Such a vapor etching device is used and a flow rate ratio of the HF vapor and water vapor, i.e., a volume ratio thereof is changed to perform vapor phase etching of the silicon wafer including a material oxide film on the surface thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a steam etching method. More specifically, the present invention relates to a method for efficiently etching away unnecessary natural oxide films, interlayer oxide films, etc. formed on the surface of a semiconductor substrate or the like in a gas phase.

(b) Prior Art Conventionally, systems have been used in which etching is performed in a hydrogen fluoride (HP) aqueous solution in pre-cleaning steps such as natural oxide film removal, and in processes such as isotropic 5102 film etching. However, with the miniaturization of devices, there has been a problem in that it becomes difficult to clean fine contact holes due to effects such as surface tension. Therefore, a cleaning method using etching in a gas phase using hydrogen fluoride vapor and water vapor has recently been developed.

This etching in a gas phase involves supplying a mixture of hydrogen fluoride vapor and water vapor to the object to be etched (usually at a volume ratio of approximately 1:
1) This is a method of etching, and it is thought that etching progresses by acting on the oxide film as shown in the following reaction formula.

H,0 5iO*+4HF, -SiF4+2Hz02+H,
O-; Length 1'l-0" +HF *Sin, ↓2H30
°+ 2HF 1-e-辷5iF4-+-4H70...
・・・・・・■ ・・・・・・■ ・・・・・・■ t0 5iF4+2HF;=辷HtSIF＠ ・・・・・・■ Here, formulas ■ and ■ are the basic reactions of reversible etching. Formulas (1), (2) and (2) represent hydration stabilization reactions in the presence of water vapor.

(c) Problems to be Solved by the Invention However, in the above-mentioned etching in a gas phase (hereinafter referred to as steam etching), HtS i Fs and 5ift produced in reaction formulas There was a problem with a large amount of precipitation on the surface.

In order to remove such a large amount of particulate matter, washing with water is required after etching, but this causes problems such as natural oxidation on the surface of the object, which is a big problem in practical use. There was a problem.

The present invention has been made under such circumstances, and particularly provides the above-mentioned etching method which allows etching to proceed while preventing or suppressing the generation of the above-mentioned particulate matter.

(d) Means for Solving the Problems According to the present invention, the oxide film on the surface of the object is etched and removed by supplying a mixture of hydrogen fluoride vapor and water vapor to the object to be etched. Volume ratio of hydrogen vapor and water vapor (HF/HtO) = O
A steam etching method is provided, characterized in that the steam etching method comprises:

This invention adjusts the ratio of hydrogen fluoride (HP) vapor and water vapor mixed and supplied in the etching process to HF/H!
This is based on the discovery that by controlling O=5 to 50, the generation of particulate matter that can occur during the etching process is significantly reduced.

The HF vapor and water vapor used in this invention can be supplied from known steam generators such as HF cylinders, HP aqueous solutions, H, O tanks, etc. HF vapor and water vapor from such a steam generator are each supplied into the etching chamber through appropriate conduits. In this invention, HF
The supply ratio of steam and water vapor is HF/H20 by volume.
=O~50, and HP/H,0=20~35 is most preferred.

These supply ratios can be controlled by adjusting the steam supply flow rate ratio. An object to be etched, such as a semiconductor wafer, is placed in the etching chamber. Here, it is preferable to configure the channel system so that the HF vapor and the water vapor are brought into continuous contact with the surface of the object to be etched in a state in which they are mixed as uniformly as possible. In this respect,
Preferably, a porous distributor is disposed between the steam inlet to the etching chamber and the object to be etched. Furthermore, instead of directly connecting each steam supply pipe to the etching chamber, it is possible to connect these to a mixing container or a mixing pipe line of a fixed capacity, and supply the steam to the etching chamber via such a mixing container or pipe line. It has also been found to be favorable.

In addition, in the etching process, the object to be etched is
The temperature is usually adjusted to 20 to 40°C, preferably 22 to 24°C. Further, the etching time is appropriately determined depending on the thickness of the oxide film and the purpose.

(E) Effect By bringing into contact a mixed gas having a HF/H,O ratio of 5 to 50, it becomes possible to efficiently remove the surface oxide film by etching while significantly reducing the generation of particulate matter.

(F) Embodiment FIG. 1 shows an apparatus for carrying out the steam etching method of the present invention. As shown in the figure, the steam etching apparatus is comprised of an etching chamber 1 having an exhaust port and wafer temperature control means (not shown), and a gas supply means for supplying mixed HF/HtO vapor into the chamber 1. The gas supply means includes an HF steam supply pipe 5 extending from the HF gas cylinder and a pipe 1 extending from the H,○ tank.
The capacity of this H20 steam supply pipe 6 connected in a facing manner is approximately 20
It consists of a gas mixing box 4 of C■3 and a gas introduction gap of 8° 8° for supplying the mixed gas from this gas mixing box into the chamber/(-1. A permeable filter 7 is disposed, and a distributor 3 made of a porous monel plate is disposed within the chamber 1. A silicon wafer 2, which is an object to be etched, is placed within the chamber 1. Etching is going on.

Using such a vapor etching apparatus, a silicon wafer (having a natural oxide film on the surface) was subjected to vapor phase etching by varying the flow rate ratio, that is, the volume ratio, of HF vapor and water vapor.

This result will be explained below.

First, the flow rate ratio of HF/H,O was varied between 1:100 and 1:100, and etching was performed under 50% overetching conditions (wafer temperature: 23°C). SI is the number of particles with a diameter of 0.16 μm or more.
Counted by MS. The results are shown in FIG.

In this way, the number of counts of particulate matter decreased to less than 20,000 counts in the range of HF/H,O of approximately 5 to 50, and especially in the range of HF/H,O of 20 to 35.
It can be seen that the count has drastically decreased to below 0 counts. In particular, the number of particles with a count of less than 1000 is lower than that of the conventional method.
This is a significantly reduced number compared to 0,000 counts, and is an acceptable number for subsequent processes.

(g) Effects of the Invention According to the steam etching method of the present invention, it is possible to perform etching removal of an oxide film while significantly reducing the generation of particulate matter caused by HtSiFa and Sin during the vapor phase etching process.

Therefore, the scope of application of steam etching can be expanded, and its impact in this field is significantly greater.

[Brief explanation of drawings]

FIG. 1 is a configuration explanatory diagram showing an example of an apparatus for carrying out the method of the present invention, and FIG. 2 is a graph diagram for explaining the effects produced by the method of the present invention. 1... Etching chamber 2... Silicon wafer, 3... Distributor, 4... Gas mixing box, 5... HP steam supply pipe , 6... H, O steam supply pipe, 7... Gas permeable filter, 8.8°... Mixed gas introduction pipe.

Claims (1)

[Claims] 1. The process involves supplying a mixture of hydrogen fluoride vapor and water vapor to the object to be etched to etch and remove the oxide film on the surface of the object.
A steam etching method characterized by supplying a mixture of HF/H_2O)=5 to 50.