JPH03167825A - Etching device and etching method - Google Patents

Abstract

PURPOSE:To perform reproducible clean etching by etching a substrate or a semiconductor thin-film of mainly Si on the substrate, raising the temperature of the substrate to 100 deg.C or higher in a vacuum, and evaporating a reaction product remaining on the substrate surface. CONSTITUTION:An SiO2 film 2 and a poly-Si 3 are stacked on a Si substrate 1, resist 4 is applied, and plasma etching is performed with Br2 gas. Then SiBr4 5, a reaction product, is produced on the sides vertical to the substrate 1. When the substrate temperature is raised to 100 deg.C in the same vacuum, SiBr4 5 evaporates into the vacuum. After that, the resist is removed with O2 plasma, and the desired patterning of the poly-Si to is finished. This method makes it possible to perform high-precision etching without lowering the yield which is caused by dust, etc. Besides, when the substrate temperature is controlled with a sensor 28 while placing the substrate 21 on a stage 23 cooled with a liquid N2, and when a chamber 24 covered with a heater 25 is kept at 70 deg.C with a sensor 26 and a measuring instrument 27 and the substrate 21 is kept at -120 deg.C, anisotropic etching can be performed without the deposition of dust.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an etching apparatus and an etching method for manufacturing high-density semiconductor devices. Although the use of bromine-based gases with excellent anisotropy when plasma etching thin films has become advantageous for microfabrication,
Furthermore, one of the major factors in this type of anisotropic etching is that plasma etching is performed in a range where the vapor pressure of the reaction product is low. Because the vapor pressure of bromide is very low, the reaction product accumulates in places such as side walls where ions do not enter, and side etching does not occur, so anisotropy is achieved. In some cases, anisotropy can be achieved by sufficiently lowering the substrate temperature. For example, when SF6 gas is used, anisotropic etching is achieved by etching at a substrate temperature of -120 degrees Celsius or less (7 degrees Celsius 10 times). Um; Proc, of 1
0thDry process Symposium.
42 (1989)).

Problems to be Solved by the Invention In plasma etching that mainly uses bromine-based gas, the use of reactive biobottoms such as SiBra, which has a very low vapor pressure, is prohibited. The raw materials with a low temperature re-deposit everywhere in the reaction chamber, including on the semiconductor substrate in the reaction chamber. Because there is ion bombardment on the flat parts of the substrate, re-deposition does not occur in this part, but re-deposition occurs in parts perpendicular to the substrate, such as the sides of the resist. When the substrate is exposed to the air, SiBrs reacts with oxygen in the air to form Si02.Also, when the resist is removed and oxygen plasma treatment is performed, it further changes to Si02.
2. Normal sulfur filth cannot be removed by hydrogen peroxide cleaning, and in the reversal process, unnecessary excess material is deposited on the substrate.Low-temperature plasma etching involves cooling and etching the substrate. In this case, reaction products accumulate on the surface inside the chamber, resulting in problems such as deterioration of etching reproducibility and increase in dust.In addition, the temperature of the chamber other than the substrate is generally not controlled. Therefore, the plasma state changes as the chamber temperature changes over time.The present invention, which was developed in view of the above-mentioned problems, has the disadvantage that the plasma state changes as the chamber temperature changes over time. Etching equipment and etching method that can achieve high-precision etching without leaving any debris on the substrate surface, or remove reaction product debris that adheres to the chamber to always achieve clean etching with good reproducibility. Means for Solving the Problems The present invention (1) solves the above problems by subjecting a semiconductor substrate or a semiconductor thin film formed on a semiconductor substrate to a semiconductor thin film containing silicon as a central element in plasma. After etching, the temperature of the substrate is raised to 100 degrees or more in vacuum to evaporate the reactive biomass remaining on the substrate surface before exposing the substrate to the atmosphere. 2) is characterized by etching in plasma while maintaining the substrate temperature at a constant temperature below zero degrees Celsius, and maintaining the chamber temperature other than that in contact with the substrate at a constant temperature above 70 degrees Celsius. Based on the above-mentioned principle (1), the present invention provides an approach to raise the substrate temperature to a high temperature without releasing the etching end ratio into the atmosphere.
High-precision etching can be achieved without the reaction product with low vapor pressure remaining on the substrate surface during etching. Also, with the above structure (2), the chamber surface is maintained at a high temperature. This makes it possible to realize anisotropic etching with good plasma reproducibility without depositing substances that cause dust on the surface. shows. In the figure, a silicon oxide film 2 is placed on a silicon substrate 1.
After depositing polysilicon 3 and forming polysilicon 3 on it, a predetermined area is patterned with resist 4 (Fig. 1a).
. Next, plasma etching is performed using Brz gas. The etching gas may be used with other gases, such as HBr, or even if the cross-sectional view in the middle of etching is as shown in Figure 1b.Substrate l
SiBr4 (5
) is clearly expressed. When the etching is completed, a side wall of SiBr4(5) is formed as shown in FIG. As a result, the SiBr4 (5) formed into sidealls is evaporated in vacuum, and no SiBr4 remains on the substrate surface (FIG. 1d). By removing the resist 4 using oxygen plasma, the target material can be removed. The patterning is completed (Fig. 1e).

Figure 2 shows the vapor pressure versus temperature curves for SiCln, TiCln, and SiBra (CRC HandBook ofC).
hemistry and physics 1984
-1985). Below, we will explain why the sidewall of SiBr4 (5) evaporates by increasing the substrate temperature to 100 degrees & The boiling point of SiBrn is 154 degrees.
The boiling point of cASiC14 is 57. Even at 57C, at room temperature (
In etching at ~20C), SiClz requires a reduced pressure in the plasma.
n is the force at which deposition occurs;
This is not the case with SiCl4.In other words, T
The vapor pressure of iCl4 at room temperature is 10 mmHg (T
orr) was Ws. To avoid this, deposits may remain below around 10 mmHg (;L
In SiBrS, it is necessary to increase the vapor pressure by raising the substrate temperature to a high temperature.For chambers that are constantly under reduced pressure, 70C (vapor pressure 10 nmHg) or higher is required.For items that are taken in and out quickly, such as wafers, it is a little more necessary. A high temperature is required, and it is not necessary to exceed the IOOC. Therefore, by raising the substrate temperature to 100 degrees, SiBr4
In the figure, a silicon substrate 2l is placed on a stage 23 cooled with liquid nitrogen 22. Even if the substrate temperature is accurately controlled by the temperature sensor A (28) and the computer (measuring device) 20, the chamber 24
is covered with heater 25 and temperature sensor B (26)
Even if the chamber temperature is accurately controlled by the computer (measuring device) 27, or the chamber is evacuated by a vacuum pump, performing RIE after accurately controlling the temperature parameters will result in good reproducibility. Perform etching. The chamber 24 itself is kept at a constant temperature of 70 degrees, which is higher than room temperature, so there is almost no adhesion of plasma polymers, etc. due to reactions in the plasma, and the polymer peels off during etching. This prevents dust from adhering to the substrate 2l.Moreover, the substrate 2l is sufficiently cooled to prevent temperature storms below zero degrees Celsius, e.g.
Since the temperature is maintained at 120 degrees, it is possible to perform etching with excellent anisotropy. However, as is clear from the above explanation, according to the present invention, there is no reduction in yield due to dust, etc. It is possible to perform etching and improve the yield of VLSI.

[Brief explanation of the drawing]

Fig. 1 is a process cross section in the first embodiment of the present invention. Fig. 2 is a characteristic diagram showing vapor pressure curves with respect to temperature in SiC1n, TiC1n, and SiBr4. Fig. 3 is an etching apparatus in the second embodiment of the present invention. 1.2 1...Silicon base slope 2...Silicon oxidation wind 3...Polysilicon, 4...Resist, 5.
...3iBra,'IO. 27...computer 2
2...Liquid nitrogen fish 23...Stage, 24...Chamber, 25...Hiku 26.28...Temperature sensor.

Claims (3)

[Claims] (1) An etching device characterized by maintaining the substrate temperature at a constant temperature of 0 degrees Celsius or lower, and maintaining the chamber temperature other than the chamber where the substrate comes into contact at a constant temperature of 70 degrees Celsius or higher. (2) After etching a semiconductor substrate or a semiconductor thin film with silicon as the main element formed on a semiconductor substrate in plasma, the substrate temperature is raised to 100 degrees or more in a vacuum before exposing the substrate to the atmosphere. An etching method characterized by evaporating reaction products remaining in (3) An etching method characterized by performing etching in plasma while maintaining the substrate temperature at a constant temperature of 0 degrees Celsius or lower, and maintaining the chamber temperature other than that in contact with the substrate at a constant temperature of 70 degrees Celsius or higher.