JPS60194524A - Controlling method of plasma treatment - Google Patents

Abstract

PURPOSE:To shorten the time for the optimization of processes regarding several blank by calculating the changes of an etching rate, shape, a selection ratio, etc. due to parameters on plasma treatment, such as gas pressure, input power, the kinds of gases, etc. without actual experiments and controlling etching treatment. CONSTITUTION:The principal cause of vertical etching is represented by the product of the reaction probability (Yai+/A) of ai<+> at energy (Ei) at a time when the particle flux of neutral particles ai and ionized particles ai of ai are projected to a fixed surface from plasma and a solid A. Since ER (vertical direction) =alphaGAMMAaiXYai/A is formed and there is etching only of neutral atoms and molecules regarding the transverse direction, an etching rate is represented by ER (vertical direction)=alphaXGAMMAaiXYai/A by the particle flux (GAMMAai) of atoms and molecules and the reaction probability (Yai/A) of ai and the solid A. Vertical and transverse etching rates at every material are obtained, the optimiztion of the conditions of etching can be drawn out by a computer on the basis of the values, and the control of etching using the computer is enabled.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for controlling plasma processing, and in particular to a method for determining etching characteristics suitable for determining an etching end point and optimizing etching conditions, and a process using the same. Concerning a control method.

[Background of the invention]

The conventional method of controlling dry etching characteristics is to detect the end point of etching by measuring plasma emission spectra, etc., and to check the uniformity of etching rate, shape after etching, and selectivity (etching rate ratio between materials) in advance. Since I was making inferences based on similar experimental results,
This method has the drawback that it requires an extremely long time period and experiments to optimize the process for each material.

[Purpose of the invention]

The purpose of the present invention is to provide a method for calculating changes in etching rate, shape 2 selection ratio, etc. due to plasma processing parameters such as gas pressure, input power, and gas type without conducting actual experiments, and to An object of the present invention is to provide a method for controlling an etching process using a method.

[Summary of the invention]

Etching by plasma can be classified into three types: etching by ions, etching by electrically neutral particles called radicals, and etching by the synergistic effect of ions and radicals. Of these, the calculation method for the etching speed of the first two is as follows:
Although it was known that the etching rate was simply multiplied by the number of incident particles and the reaction probability of each particle, there was no way to calculate the etching rate due to the synergistic effect of ions and radicals, which is the main cause of the etching rate. The present invention is to discover a method of enhancing the synergistic effect of ions and radicals, and to control reactions caused by plasma based on this method.

[Embodiments of the invention]

The etching characteristics of dry etching are determined by the etching rate, selectivity, and shape, and these are expressed by two factors: the etching rate in the depth direction and the etching rate in the lateral direction parallel to the sample surface. Regarding reactive ion etching, when etching in the depth direction is replaced with etching in the vertical direction, the particles in the plasma that perform the vertical etching are positively charged ions, gas molecules, and two molecules of atoms generated from gas decomposition. be. On the other hand, in the lateral direction, there is no contribution from cations, and electrically neutral atoms 9
It is done by molecules. Therefore, as a first approximation, the vertical etching speed is the sum of the etching speed of ions incident perpendicularly to the solid and the etching speed of thermally moving neutral particles (two M molecules), and the etching speed of the synergistic effect of these. Therefore, the lateral direction is expressed only by the etching rate by neutral particles.

The longitudinal etching rate (ERA) is determined by the ionic species (al”
) incident particle J flux (rat” (pieces/al −5ee)
).

Reaction probability between etched material A and ion species a1+ at ion incident energy Ei (Yak''/A) p Particle flux of neutral particles (ai) (rat (pieces/c+# -sec)
) and reaction probability between al and etching material A (Yat/A)
Using ER vertical = a X I' a t ” X Y at
+/ A+ (Z r a i XYa+/A + (synergistic effect) The etching rate of these two terms is
1 of the etching speed in actual reactive ion etching
It was found that only a value of /10 or less was shown. In other words, the main cause of vertical etching is the synergistic effect of the third term, and in the present invention, this term is defined as when the particle flux of neutral particles a1 and the ionized particles a1 of Al are incident on the fixed surface from the plasma. a1+ and fixed A at the energy (El) of
This is based on the finding through experiments that the reaction probability is the product of the reaction probability (Ya++/A). That is, ER vertical = a r at X Y at + / A
(2) becomes. We will discuss how to apply this new knowledge to experimental plasma etching.

In actual plasma, molecular gas (Ax B y )
becomes plasma, and the gas molecules decompose into various forms.

Therefore, al shown in formula (2) represents all the atoms and molecules produced by its decomposition, and the etching rate is given by the sum of them. Therefore, by fixing the generated particles,
This discovery allows us to understand the vertical etching speed of etching using plasma.

In the lateral direction, since only 9 molecules of neutral atoms are etched, the etching rate is determined by the particle flux of atoms and molecules (rar) and the reaction probability between al and solid A (Ya+/A
), ER vertical = αX ras X Y at / A
(3) becomes.

That is, rat and Y al ” / A I Y a
, /A, the etching speed of the material to be etched A in the vertical and horizontal directions can be calculated from equations (2) and (3).

According to the present invention, based on the above considerations, it is possible to determine the etching speed in the vertical and horizontal directions for each material, and to derive the optimization of etching conditions using a computer based on the values.
Etching can be controlled using a computer.

An embodiment of the present invention will be explained with reference to FIG. 1 and Table 1. This embodiment describes an etching control method when etching Si with CF 4 gas plasma using a parallel plate type high frequency discharge plasma etching apparatus.

Table 1 Table 1 shows the composition ratio of two molecules of atoms generated in CF4 gas plasma, the incident particle flux of each neutral particle when the degree of vacuum is 10 Pa, and the ion F+ of each particle,
CF3+, CF, +, CF”.

The probability of reaction between C+ and St when the ion energy is 200 eV is shown. The particle composition ratios shown in Table 1 are:
Degree of vacuum: 10 P, input power: 100 W (frequency: 1
3.56 MHz). The incident particle flux is CF
The rate at which four gases are decomposed into nine atoms and molecules is determined from the change in the degree of vacuum before and after discharge, and in this case, 1% of the total is decomposed. When the input power was increased from ioow to 150 W, the decomposition rate increased by 3/2 to 1.5%, indicating a linear relationship with the input power.

The reaction probability between each ion F `` y CF 3 '' y CF z+ and Ss changes depending on the ion energy as shown in FIG. 1. Furthermore, the ion energy that reaches the Si surface within the etching apparatus changes depending on the degree of vacuum and input power.

The ion energy is approximately equal to the difference between the potential of the Si surface or sample stage and the ground potential. Therefore, by determining the ion energy by measuring the potential, and calculating the reaction probability between the ion and St using FIG. 1, the probability of a reaction occurring depending on the degree of vacuum and the input power can be determined.

The reaction probability shown in Table 1 is a value at an ion energy of 200 eV under the conditions of 10 Pa and 100 W.
It was possible to increase the St etching rate using gas.

Here, the points to be particularly careful about in calculations are the C atoms and CF molecules produced by the decomposition of CF4 gas, as well as CF2. CF3
C contained in the molecules is deposited on the Si surface as shown in FIG. Therefore, F atoms will be used to remove deposits from the surface. F shown in Figure 1
The reaction probability between + ions and C film did not change with respect to ion energy, and was 0.33 ions/ion.

Here, in FIG. 2, it can be seen that almost all C+ is deposited on the surface. Therefore, in the CF3 molecule, C contained in the molecule is deposited, and all three F atoms in the molecule are used for etching. In the case of CF 2 , the F atoms are added by one, and therefore the F atoms generated in the plasma are used. In the CF molecule, there are two F atoms and, in the case of C atoms, three r? JJI child is necessary.

By subtracting the F atoms required to remove the above deposits from the total Fg atoms, the F atom particle flux used for St etching can be calculated.

As a result of calculation, under the conditions of this example, 70% of the total F particle flux is used for C removal, and 30% of the total F particle flux is used for etching Sj.
It became clear that F of % was used, and the etching speed in the vertical direction at that time was found to be 1700 people/win. Also, in the horizontal direction, the number was 100 people/win.

In this example, the above calculation was programmed and a computer was used to derive the etching speed. In this method, by providing the necessary basic data such as reaction probability and ion energy, it is possible to very easily determine the relationship between etching conditions and etching results, and to set the etching conditions and determine the etching end point. It was extremely effective.

The present invention is directed to metals such as 80, W, and Mo, and compounds containing at least one of these materials, that is, AQ-C.
u, An-Cu-8t, AM-Ni.

In the W-8ts Mo-5i, it was also possible to control a computer based on a program to set etching conditions and determine the end point of etching, and to determine the conditions of an etching apparatus using the output of this computer.

Furthermore, it can be applied to mask materials such as inorganic resist materials and organic resist materials, and insulators such as SiO□ and Si3N. It was extremely easy to set the conditions for the manufacturing process and determine the end point of etching for a semiconductor device having the following properties. In addition, the selectivity (etching rate ratio) was also clarified at the same time.

As the etching gas, CF4t SFe vNF
3 grade fluorinated metal gas, ccQ,.

S i CQ 4 , B CQ 3 chloride gas, C
BrF3°C, CQ F5, C2 (gases containing two or more halogens such as 12F4, as well as CHF3 and CH2
A compound gas containing halogen and hydrogen such as Fz could be applied. It is also possible to add O2, N2, or H2 gas, and it has become extremely easy to set etching conditions even when two or more gases are mixed.

〔Effect of the invention〕

The present invention is effective in controlling etching not only in plasma etching equipment but also in ion beam etching equipment, which is a semiconductor surface treatment equipment that uses a mixture of ions and gas.

Furthermore, it can be applied to a plasma etching apparatus using microwaves, and the etching characteristics can be extremely easily controlled.

[Brief explanation of the drawing]

Claims (1)

[Claims] In a semiconductor device etching process using plasma or a mixture of gas and charged particles and an ion beam, the device etching rate by the plasma is expressed as the particle flux (unit time) of neutral particles (A) generated in the plasma. (number of electrically neutral particles incident on a unit area) FA and the incident energy of the ionized particles A+ of the neutral particles A on the element surface (B) and the ions A+
Probability of chemical reaction with Y A+ ,, which multiplication (rA
Y A-/! l), and based on the calculated etching rate.