JPS6369987A - Dry etching apparatus - Google Patents

Abstract

PURPOSE:To regulate an etching shape under a mask, by providing a means for calculating the distribution angle of plasma ions incident on a base plate by means of ion density of plasma, electron temp. and electric potential of plasma, self-bias voltage of an electrode and the density of gas for forming plasma or the like. CONSTITUTION:Self-bias voltage Vdc generating on an RF electrode 2 provided with a sample 6 is inputted to a measuring apparatus 8. A probe terminal 10 is impressed with voltage from a variable voltage source 11 and current-voltage characteristics of plasma are measured with an ammeter 12 and a voltmeter 13. Electron temp., ion density and potential of plasma are calculated from this measured valve in an arithmetic unit 14 and inputted to memories 15-17. The impressed voltage of a sheath region is calculated from the value of the measuring apparatus 8 and the memory 17 in an arithmetic unit 18, memorized 19 and also indicated on an indicator 20. Further sheath width is calculated from the value of memories 15, 16, 19 in an arithmetic unit 21 and memorized 22. Furthermore the gas pressure of a reaction chamber 1 is measured with a manometer 23. These value is inputted to an arithmetic unit 28 and the angle distribution of ions is calculated and indicated 29.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to a dry etching apparatus using reactive ion etching to uniformly adjust the etching shape under the mask of a substrate covered with a mask. This invention relates to a dry etching device that can be used for dry etching.

[Conventional technology]

In conventional dry etching, reactive ion etching (
(hereinafter abbreviated as RIE) is widely used.

Since the RIE plasma generation mechanism and the etching Ill are connected to each other, they cannot be controlled independently, and RF force is applied to improve etching stability and reproducibility. A method is used in which the RF 11 pressure at li[ is monitored and the RF 11 pressure is controlled or the gas pressure is controlled so that the value remains constant. Also, RF? ! Devices (such as those shown in FIG. 3) are known that can monitor the occurrence of I-poles.

The dry etching device is installed in the reaction chamber (R).
An RF i source (&l
Input power to RF electrode (2) and ground? +! ff
i (the sample side placed on the RF electrode by generating plasma between the RF electrode and the RF electrode), and the Vdc generated at the RFT (, 2) is transmitted through the attenuator (7). It can be displayed on a Vdc display device. Here, the reaction chamber (ha, earth 1! pole (51
and RF m source (4'l is connected to ground (9). Under normal RIE conditions, the absolute value of Vdc is several hundred Vol.
Since t, use the attenuator (7) to T: Vdc//
It is widely used to attenuate the signal to about l 000 and display it on a VDC display device with a built-in oscilloscope or the like. Here, the above dC is equivalent to the potential difference in the sheath region generated between the plasma region and the RF electrode (2), and therefore serves as a guideline for the acceleration voltage of ions that cross the sheath region and enter the sample (B). It is known.

[Problem that the invention seeks to solve]

However, the conventional dry etching apparatus described above has a serious problem in that it is not possible to monitor the angle of incidence of ions on the sample, which is necessary when forming a fine pattern with a submicron width on a substrate using a mask.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a dry etching apparatus that etches a substrate using plasma generated by applying high frequency power to a plasma generating gas in a reaction chamber.
From the measurement results of the probe terminal, the plasma ion density n
1, an arithmetic unit that calculates the plasma electron temperature Te and plasma potential ■p, a measuring device that measures the self-bias voltage Vclc of the Mi cell on which the substrate is installed, a gas pressure measuring device that measures the pressure inside the reaction chamber, and the gas pressure. A computing unit that calculates the density n of the plasma generation gas in the neutral state in the reaction chamber from the measurement results of the measuring instrument, the ion density ni of the plasma, the electron temperature Te of the plasma, the plasma potential vp, and the self-bias potential v
A computing unit is provided for calculating the angular distribution of plasma ions incident on the substrate from dC and the density n of the plasma generating gas in a neutral state.The above computing units may each be provided with an independent computing unit. It may be provided in such a way that it is shared by large-sized processors.

[For production]

Ions generated by the plasma must cross the sheath region and enter the sample. Gas pressure is 0. /TO
Taking the Ar plasma of rr as an example, the sheath width and the mean free path of the ions are both on the order of /, so the probability that the ions will collide with neutral particles while traveling through the sheath region cannot be ignored. This probability increases further under conditions of thick sheath width and high gas pressure. Here, the probability P of an ion colliding with a neutral particle before it enters the sample is calculated using the DC discharge model, taking into account that the ion-neutral particle collision cross section σ depends on the kinetic energy of the ion. Expressed as a time average by P −/−exp
(-dis/l□ + 5P tr(x')/lr□
rlx'). However, in equation (1), dis: sheath width lo: mean free path of ions at the sheath entrance f(x))
: Collision cross-sectional area at location xi within the sheath (Xt is normalized by the sheath width dis) G0: Collision cross-sectional area at the sheath entrance. Therefore, the collision probability P is the sheath width dis.

Mean free path 10. It can be determined from the My projection area tr(x〆).

First, the sheath width d is the Lang
It is expressed using the muir-Child equation. However, in equation (2), ε0: Vacuum permittivity e': natural logarithm b
asee: Elementary charge k: BO1tZman constant Te: Electron temperature vp: Plasma potential VaC: Sheath bias voltage It can be calculated from the ion density ni. Here, Te,
Vp and ni can be measured by the Longmuir probe method. Further, as explained in the conventional method, VaC can be determined from the value displayed on the oscilloscope hoop.

Next, the mean free path lo is given as 10-y7nv(, Is) from the following equation. However, in equation (3), n: density of neutral particles σ0: collision cross section at the sheath entrance. Here, the density n of the neutral particles can be easily determined from the gas pressure of the RIE apparatus.

Furthermore, the collision cross-section inside the sheath σ(x') is expressed by the change cr (Vl) in the plane bump cross-section due to ion kinetic energy and the potential distribution V(x') in the sheath. Using the fact that σ(■ is expressed by Child's equation) from known data, the collision cross section σ<xt> at any location within the sheath can be determined.

That is, the collision probability in equation (1) can be determined from the measured value of the plasma state and the known data of the collision cross section. Next, we derive the expression for the angular distribution of ions.

Here, ions that are scattered by neutral particles and obliquely enter the sample include those that are scattered only - times and those that are scattered twice or more. Therefore, multiple scattering must be taken into consideration when determining the angular distribution of ions obliquely incident on the sample. However, when the sheath region ais is shorter than the mean free path 10 (dis<<lo), the majority of ions are scattered - times, so it can be approximated that the ions are scattered - times. Here, Q
-Probability of sipping P(x) ax is P(x)d, r−k
(,r)d,re,rp(-fSlSl((rldx
) (expressed as 41. However, in equation (4), k(xl: collision coefficient at location X within the sheath.) When integrating equation (4) over the sheath region (o, dis), The collision coefficient k f,rl is the product of the neutral particle density n and the collision cross section f(,r) at location X, and k(,rl-n・σ(
x) (Using the expression 51 and further setting xt-xla1S, equation (1) is obtained.

The velocity of ions on the sample surface is expressed by the quality number of the ions, the velocity of the ions after scattering, and the sheath electric field (determined from the sheath potential distribution v (x'>) described above. Using this, it is possible to The angular distribution f of the incident ions can be calculated. Here, the velocity of the ions after scattering is determined from known data of the ion-neutral potential that describes the scattering.

The dry etching apparatus of the present invention has the above ion density n1
Since we have measuring instruments for each variable such as 9% prehumidity Te, plasma position vpl sheath bias potential VaC, and neutral particle density pn, we can measure the known plasma ion species,
The angular distribution f(θ] can be calculated based on the following formulas:

〔Example〕

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

FIG. 1 is a schematic block diagram for explaining one embodiment of the present invention. (1) is the reaction chamber, (2) is RFX! .

(3) is a matching device, (4) is an RF oscillator, (5) is an earth clamp, and (6) is a sample. ) through the RF oscillator (to generate a plasma between the above RFII! pole (2) and the ground electrode (sample -))
Perform etching.

The self-bias voltage ■dC generated at the RF electrode (2) where the sample (B) is installed is reduced to V via the attenuator (7).
Input into a dc measuring device. Here, dc is the DO pressure generated at RF voltage & (, !1, so it is drawn with a Vdc measuring device (the one with a built-in oscilloscope) - temperature Te + ion density n1. plasma potential Vp can be measured by the Langmuir probe method.A voltage is applied from a variable voltage source (/l) to the probe terminal (10) installed in the reaction chamber (1), and an ammeter (/2), M
The current-voltage characteristics of the plasma are measured using an i-pressure meter (13). Input this measured value into the calculator (C), and
Te + n i + Vp is calculated from the voltage characteristics and each is input into the memo IJ (/j) to (17). In Figure 1, the memory of Te is (/j), the memory of ni is (#), and the memory of V
The memory of p will be explained as (17). Here, Te.

For information on how to calculate ni and Vp, see Yoshinori Heda's ``
There is an explanation on pages 6 to 30 of ``Gas Discharge'' (Kinda Kagakusha).

(#), (/9) to the arithmetic unit (F/)K input, (2)
The sheath width dis in the formula is calculated by the arithmetic unit (21) and input into the memory (2). The gas pressure in the reaction chamber (1) is measured by the gas pressure gauge (23), and the ion-neutral particle collision cutoff m1 product σ○ at the sheath inlet is input, and tf□ is read from the memo IJ (,!40). Then, the mean free path 20 at the sheath entrance is calculated from equation (3) using the computing unit (25).The calculation result of the computing unit (2) is calculated as Based on the principle of this example, all 10 are calculated and can be calculated from the memory (/9), (here), (here) and other known data of the ion-neutral potential that describes ion scattering. As explained above, the memory (27) and the memory (/9) into which the known data of the ion-neutral particle potential are input.

C22), (26) are input to the arithmetic unit (28) and (ge)
The angular distribution of ions is calculated from the formula and displayed on the display device (29).
to be displayed.

Cloth can be displayed on each display device #(20), (Jri).

Figure 1 shows the results obtained by simulation of the angular distribution f(of obliquely incident ions in Ar plasma using the method described above. However, the change in the collision cross section due to the incident energy of the ions is Experimental data of Ar (W, H, Oramer: J, Chemphys
, LL, g≠/(/q1)), sheath @di
When the ratio of s to mean free path lo is dis/l□-0,/, the angular distribution f(is, and the total number of obliquely incident ions is 7
f(). Note that the case where ions are perpendicularly incident on the sample is defined as θ-00.

In the above embodiment, the result calculated by the calculator (28) is displayed on the display device (2q), but the high frequency voltage, gas pressure in the reaction chamber, etc. are controlled based on the calculated result. It is also possible to consider an apparatus that does not have a display device or the like, but is equipped with a control circuit for the purpose of controlling the image.

[Effect of idea]

It is possible to calculate the incident angle of ions on the sample surface online, which was not possible with odor. Furthermore, according to the present invention, when etching a pattern with a width of submicron using a mask, it is possible to prevent the angular distribution of the ions entering the substrate through undercuts under the mask by monitoring, thereby ensuring good etching. can be carried out.

[Brief explanation of the drawing]

Fig. 1 is a noflock diagram of an example of the dry etching apparatus of the present invention, Fig. 2 is a simulation result of the angular distribution f(θ) calculated using the dry etching apparatus of the present invention, and Fig. 3 is a diagram of a conventional dry etching apparatus. It is a block diagram. Figure 2 Incident angle θ (degree) Figure 3

Claims (1)

[Claims] (1) In a dry etching apparatus that etches a substrate using plasma generated by applying high frequency power to a plasma generation gas in a reaction chamber, a probe terminal (10) for measuring the state of plasma, and measurement of the probe terminal a computing unit (14) that calculates the plasma ion density ni, the plasma electron temperature Te, and the plasma potential Vp from the results;
A measuring device (8) that measures the self-bias voltage Vdc of the electrode on which the substrate is installed, a gas pressure measuring device (23) that measures the pressure inside the reaction chamber, and a neutral state of the reaction chamber based on the measurement results of the gas pressure measuring device. A computing unit (25) that calculates the density n of the plasma generation gas from the ion density ni of the plasma, the electron temperature Te of the plasma, the plasma potential Vp, the self-bias potential Vdc, and the density n of the plasma generation gas in a neutral state. A dry etching apparatus comprising: a computing unit (28) for calculating the angular distribution of plasma ions incident on a substrate.