RU2456702C1 - Method for plasmochemical etching of microelectronics material - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: in the method for plasmochemical etching of microelectronics material, the material is placed on a substrate holder in a vacuum chamber, working gas is fed into the vacuum chamber, plasma is ignited via radio-frequency induction discharge and radio-frequency power is fed to the substrate holder. Etching is carried out with division into repeating cycles. Each cycle consists of two phases: etching and passivation, wherein during the etching phase, radio-frequency power is fed to the substrate holder in the range of 208-300 W for 0.1-100 s, and at the passivation phase - in the range of 100-120 W for 0.1-40 s.

EFFECT: such etching conditions enable to improve uniformity of etching 2,5-3,5-fold while maintaining the rate of etching.

2 dwg, 1 tbl

Description

The invention relates to methods for processing materials of microelectronics, and can be used in the production technology of electronic components for micro and nanosystem technology.

Currently, in this area a widespread method of plasma chemical etching. The characteristic of the method depends on many parameters: pressure, power, RF bias potential, composition of the working gas, duration of passivation and etching, etc. Therefore, depending on the material of specific products, the optimum etching mode is selected in order to obtain a high-quality surface.

A known method of plasma etching above a substrate, including placing the substrate on a substrate holder in a vacuum chamber, supplying a source gas, plasma formation and a cyclic etching process (RF patent No. 2339115, IPC H01L 21/3065, 2008).

In the known method, the cyclic etching process is an alternating operation of periodic modulation of gases and etching operation. In addition, each etching operation includes a reactive etching gas supplying step and a plasma forming step from the supplied etching gas.

The disadvantages of this method include the fact that it does not provide an acceptable etching rate. Etching is carried out with high energy bombarding the surface of the ions, which can degrade the surface quality and increase the number of introduced defects.

A known method of etching a substrate placed in a vacuum chamber on a substrate holder by supplying a working gas to a vacuum chamber, generating a plasma, the etching operation is carried out in repeated cycles, each of which consists of several stages (RF patent No. 2332749, IPC H01L 21/3065, 2008).

The disadvantage of this method is the insufficiently high surface quality. This circumstance is explained by the fact that plasma is generated by applying high-frequency power to the substrate holder. As a result, the ions bombarding the surface of the substrate gain high energy and, as a result, surface quality deteriorates and a large introduced defect occurs.

The closest technical solution to the claimed combination of essential features includes a method of plasma-chemical etching of microelectronic materials, including placing the material on a substrate holder in a vacuum chamber, supplying a working gas to a vacuum chamber, igniting a plasma by RF induction discharge, supplying RF power to the substrate holder and etching (patent RF №2090951, IPC H01L 21/3065, 1997 - prototype).

The disadvantage of the prototype method is the poor etching uniformity of 5% at an etching rate of 0.4-0.6 μm / min.

This may be due to the fact that the etching process is carried out at a very low pressure and high plasma concentration with a magnetic field, which leads to the appearance of a boundary effect and a deterioration in the etching uniformity across the plate.

The present invention is to increase the etching uniformity while maintaining the etching rate.

The problem is solved due to the fact that in the method of plasma-chemical etching of microelectronic materials, including placing material on a substrate holder in a vacuum chamber, supplying working gas to a vacuum chamber, igniting a plasma by RF induction discharge, supplying RF power to the substrate holder and etching, etching is carried out with separation into repeating cycles, each of which consists of two stages: etching and passivation, while at the etching stage, the RF power is supplied to the substrate holder in the range of 280-300 W s 0.1-100 s, at step passivation - in the range 100-120 W for 0.1-40 s.

The technical result is achieved due to the fact that the etching operation is carried out in the form of a cyclic two-stage process. Moreover, each cycle consists of a stage of etching and passivation. By adjusting at both stages the mode of supplying the quantity and duration of the RF power to the substrate holder, the etching uniformity can be significantly improved. This is possible because at the first stage - etching, the ion energy is high and they act on a par with chemically active particles, making a significant contribution to the etching process. At the second stage - passivation, the ion energy is minimal and the ion bombardment of the material is much less efficient, which allows the formation of a passivating fluorocarbon polymer layer on the surface of the material, which is partially removed during the etching stage, including high-energy ions, and thereby has a leveling effect.

The invention is illustrated by the diagram of the vacuum chamber (figure 1).

The vacuum chamber consists of a casing 1, a reactor with induction plasma excitation (ICP antenna) 2, a substrate holder 3, a substrate (material) 4, generators GHF-1 and HHF-2.

Examples of the method

Example 1

Plasma-chemical etching of a series of piezoelectric quartz parts with a diameter of 2 mm and a thickness of 66 μm was carried out on a Carolina PE 15 vacuum unit shown in the diagram.

The substrate 4 in the form of a series of piezoelectric quartz parts, coated with a copper ring mask with a chromium sublayer, was placed on a substrate holder 3. The initial temperature of the substrate holder was 22 ° C. Through a special gateway, the substrate holder 3 was sent to the chamber of reactor 1. Then, C ₄ F ₈ gas was supplied to chamber 1 with a flow rate of 2.5 l / h, the pressure in the reactor was set to 1 × 100 Pa. Then, using a high-density plasma generator connected to the ICP antenna 2, an RF induction discharge was ignited at a frequency of 13.56 MHz and the power invested in the discharge was set to 400 W. To increase the plasma density, a direct current of 1.9 A was applied to inductive coils located outside the reactor. Then, an alternating voltage of 13.56 MHz was applied from the generator to the substrate holder. At the first stage — etching, the power invested in the substrate holder was 300 W, the autoset voltage at the same time was 180 V, and the duration of the stage was 50 s. At the second stage - passivation, the power invested in the substrate holder was 100 W, the autosetting voltage was 40 V, and the duration of the stage was 10 s. The number of cycles is 20.

The main indicators of the process are etching rate, etching unevenness. The etching rate of a piezoelectric crystal was determined by the change in the resonant frequency of a single crystal due to a decrease in its thickness as a result of etching over a known time.

The etching unevenness was determined by the formula:

(h ^max -h _cf ) 100% / h _cp ,

where h ^max is the maximum depth of the piezoelectric quartz step in the series (microns);

h _cp is the average depth of a step in a series (μm).

Example 2

It was carried out on the same equipment as in Example 1, but a silicon wafer with a diameter of 100 mm was etched with the necessary pattern formed by photolithography. In this case, at the first stage — etching, a power of 288 W was supplied to the substrate holder for 20 s; at the second passivation stage, 111 W power was supplied to the substrate holder for 5 s.

Example 3

It was carried out analogously to example 1, but a silicon wafer was thermally oxidized to SiO ₂ to a depth of 1 μm. In this case, at the first stage, 281 W power was supplied to the substrate holder for 70 s, and at the second stage, 119 W power was supplied to the substrate holder for 30 s.

It should be noted that the implementation of the method in the mode when the power parameters on the substrate holder and the duration of the steps are below the lower stated limits, the etching process may completely stop after some time due to the excess deposition rate of the fluoropolymer over its removal rate. At parameters above the stated limits, the formation of numerous defects leads to a deterioration in surface quality.

The etching results of the examples are presented in the table.

As can be seen from the table, the technical result is expressed in improving the etching unevenness by 2.5-3.5 times while maintaining the etching rate.

In addition, the claimed method is illustrated by a diagram of two cycles for example 1 (figure 2).

Table Example 1 Example 2 Example 3 Prototype Stage 1 Stage 2 Stage 1 Stage 2 Stage 1 Stage 2 Cycling Yes Yes Yes no Number of stages 2 2 2 - Frequency of plasma generators, MHz 13.56 13.56 13.56 40-500 The frequency of the bias generators, MHz 13.56 13.56 13.56 13.56 The power invested in plasma, W 400 400 400 350 Power on a substrate holder, W 300 one hundred 288 111 281 119 - Auto displacement, V 180 40 167 53 150 62 60 Duration of steps, s fifty 10 twenty 5 70 thirty - Working pressure, Pa 1 × 10e0 1 × 10e0 1 × 10e0 2 × 10e-2 The etching rate, microns / min 0.4-0.5 0.4-0.6 0.5-0.6 0.4-0.6 Uneven etching,% ± 0.8-1.2 ± 1-1.3 ± 1.2-1.3 ± 3-4

Claims (1)

A method for plasma-chemical etching of microelectronic materials, including placing the material on a substrate holder in a vacuum chamber, supplying working gas to a vacuum chamber, igniting a plasma by RF induction discharge, supplying RF power to a substrate holder and etching, characterized in that the etching is carried out with separation into repeating cycles, each of which consists of two stages: etching and passivation, while at the etching stage, the RF power is supplied to the substrate holder in the range of 280-300 W for 0.1-100 s, at the passivation stage and - in the range 100-120 W for 0.1-40 s.

Images