JPS60198827A - Laser beam etching method - Google Patents

Abstract

PURPOSE:To etch Si vertically in the cross section while preventing damages by applying ion beams simultaneously when etching Si and SiO2 disposed in the atmosphere of fluorine or chlorine gas with radiation of excimer laser beams of XeBr, XeCl or XeF. CONSTITUTION:A material 41 of Si and SiO2 is disposed in a vacuum device 40 and chlorine or fluorine gas is introduced into the device 40 through a gas inlet tube 42. Under this condition, laser beams 45 from a laser 44 arranged outside the device 40 are applied onto the surface of the material 41 via a rotary reflecting mirror and a window 46. The laser 44 will be an excimer laser of XeCl or XeF when chlorine gas is used, and of XeBr when fluorine gas is used. Activated etchant 47 is produced within the device 40 to excite the electronic state of the Si on the material 41, while the SiO2 which absorbs the beams is not etched. Ion beams 49 from an ion source 48 are simultaneously applied to the material so that the Si is etched vertically in the cross section.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a laser beam etching method used in an electronic device manufacturing process. The process tends to shift from wet etching to dry etching, and examples of this technology include J, L,
Vossen, J. Electrochem.

8ci, Vol. 126. IQ7Qf/T)-31
0A-T)-Q9, IF-r-f → Glow discharge J in Zuma etching and plasma transition
(”Glow Discharge Phenom
enaine Plasma Etching and
Plasma etching according to a paper published entitled "Plasma Deposition"), C.J., Mog.
J by ab, A, C, Aolama, D, L Flam.

Appl, Phya, vol, 49.1979P
, 3796-P, rst at 3803.

Plasma etching of SiO2
Parallel plate type dry etching using high frequency discharge according to a paper published entitled A etching of Si and 8102), and D, J, 5harp,
J, Pantz, D, M, Mattox, J, Vac, Sci, Technol, vol.
, 16, 197 Kui P, 1879-P, 1882.
uman ton 5source to low en
Examples include ion beam etching according to a paper published under the title "Ergy").In these dry etchings, gas molecules and gas atoms containing halodane such as fluorine and chlorine, and their radicals or ions generated by electric discharge are used. Etching of Si was proceeding due to adsorption and irradiation on the surface of the St coat.@However, when manufacturing electronic devices, these molecules, atoms, radicals, and ions are also adsorbed and irradiated onto the 5in2 surface. Since etching progresses with the addition of physical impact, Si, 5i in the conventional etching method
The etching rate selectivity of 02 is brought about only by the difference in chemical reactivity of one atomic molecule, radical, or ion with St and 5IO2. For this reason, the conventional method has the disadvantage that a high selectivity cannot be obtained.

In the case of parallel plate type equipment and f-lasma etching equipment, under etching conditions that provide a vertical etching cross section, Si+
The etching rate selectivity of 8102 was approximately 10 to 15 times that of St at most. In a parallel plate type device, a selection ratio of about 60 times can be obtained if the gas is selected, but in that case, the side etch under the mask was large in the case of 2, and a simple etched cross section could not be obtained. In ion beam etching, side etching under the mask is less likely to occur, but the physical sputtering effect becomes stronger and the selectivity decreases. Furthermore, in general, ion beam etching requires ion acceleration energy as high as 500 eV to 1 keV, so that a lot of damage is caused to the sample due to ion bombardment.

[Purpose of the invention]

It is an object of the present invention to provide a method for dry etching of Si, which has a high etching rate selectivity, has a vertical etching cross section, and is less likely to be damaged by etching, and can directly etch any fine area with a good etching rate selectivity. purpose.

[Structure of the invention]

In the present invention, for St in a fluorine gas atmosphere or a chlorine gas atmosphere, XeBr excimer-f, Xe
This is a laser beam etching method in which etching is performed by irradiating a CL excimer laser and at the same time irradiating a low energy accelerated ion beam. [Detailed description of the configuration] In the present invention, By adopting the above-mentioned configuration, the problems of the prior art in that the etching rate selection ratio is low, the problem that damage remains on the etched object, and the problem that the etched cross section is not vertical are solved simultaneously.

In the present invention, three types of methods are possible by selecting the type of gas and the type of laser. The first method is to irradiate Si, 5in2 in a chlorine gas atmosphere with an ecA excimer laser, and the second method is to irradiate St, 5in2 in a chlorine gas atmosphere with a XeF excimer laser. The third method is to irradiate Si + 5102 in a fluorine gas atmosphere with a XeBr excimer laser. In the third method, the XeBr excimer laser has an output at 282 nm.

Figure 1 shows the absorption coefficients of chlorine and fluorine in the wavelength range where these three types of lasers have output, where the horizontal axis is the wavelength (nm) and the vertical axis is the absorption coefficient (, -'). be. 11
is the absorption coefficient of chlorine, 12 is the absorption coefficient of fluorine, and 1
The wavelengths shown in 3 and 14.15 are xeCt excimer laser, XeF excimer V -f' -XeBr, respectively.
There are several output wavelengths of excimer lasers. As can be seen from Fig. 1, the absorption coefficient 11 of chlorine has a value of -1 near 330 nm, and the output of the XeCt excimer laser is 308 nm.
The absorption coefficient of the XeF excimer laser is large even at 352 nm. Therefore, in the first method of irradiating XeCt excimer laser in a chlorine atmosphere, chlorine is 308
It decomposes into chlorine radicals by light absorption at nm. Furthermore, in the second method of irradiating the X@F laser in a chlorine atmosphere, chlorine is decomposed into chlorine radicals by light absorption at 352 nm. As can be seen from FIG. 1, the absorption coefficient 12 of fluorine has a peak around 280 nm, and this wavelength is equal to the output wavelength 28 of the Xe Br excimer laser.
It almost corresponds to 2 nm. For this reason, X in a fluorine atmosphere
In the third method of irradiating with eBr excimer laser, the radicals become ions by light absorption at 282 nm. Although the absorption coefficient of fluorine is smaller than that of chlorine, fluorine is more active against St.

FIGS. 2 and 3 show the absorption coefficient and transmittance of St in this wavelength range. The horizontal axis in Figure 2 is the wavelength (nm
), the vertical axis is the absorption coefficient (,, -1).The absorption coefficient 21 of Si has a peak in this wavelength region and shows a large value overall, whereas in this wavelength region the absorption coefficient of 5iO7 is approximately O (cm-').

Further, the horizontal axis in FIG. 3 is wavelength (nm), and the vertical axis is transmittance (a). 31 is the transmittance of SiO2, whereas in this wavelength range, the transmittance of Si is approximately 0%. 22, 23, 24 and 32 shown in Figures 2 and 3
, 33.34 are the output wavelengths of the XeCA excimer laser, XeF excimer laser, and XeBr excimer laser, respectively. As shown in Figures 2 and 3,
In the wavelength range of 200 nm to 420 nm, Si has large absorption, but 5102 is mostly transparent, so XeCL excimer lasers and X
Only the electronic state of Si can be excited by irradiation with eF excimer laser or XeBr excimer laser. In this way, si and 5102 placed in a chlorine atmosphere are irradiated with a XeCL excimer laser or XeF excimer laser, or si and 5IO2 placed in a fluorine atmosphere are irradiated with a XeBr excimer laser. Particularly, chlorine gas or fluorine gas becomes active by absorption of laser light, and at the same time St.
absorbs laser light of the same wavelength and becomes excited. On the other hand, StO□ does not absorb light in this wavelength range, so it remains in its ground state and does not change. Therefore, by irradiating the laser beam, chlorine or fluorine as an etching species can be activated to increase its reactivity with the object to be etched, and at the same time, by irradiating the same laser beam, only the electronic state of St can be excited and the active etching species can be etched. can assist in the reaction. As a result of the synergistic effect of this absorption of chlorine and absorption of Si, only the Si in the sample soil is etched by v = laser beam irradiation, and almost no SiO□ is etched, resulting in etching with a good etching rate selection ratio of Sl to SiO3. It can be carried out.

Now, in the present invention, an ion beam is irradiated with an ion beam at an acceleration energy of 50 eV to 200 eV, which is lower than the usual one, to the Si, 5to2 which performs the laser beam etching as described above. As a result, the anisotropy of etching can be increased and vertical etching conditions with less side etching can be obtained. In this case, since the acceleration energy of the ion beam is low, the loss of secretion due to ion bombardment occurring on the ion beam receiving surface is extremely small. Furthermore, by appropriately selecting the output of the laser beam, damage to the irradiated surface by the laser beam can be suppressed.

Furthermore, depending on the focusing state of the laser beam, the present invention can be used in two types of etching methods. The first is the etching of a relatively wide sample area by irradiating a laser beam all at once, and the second is the direct etching of an arbitrary minute sample area by condensed laser beam irradiation. In either case, the etching using a combination of a laser beam and an ion beam in a chlorine or fluorine atmosphere according to the present invention as described above has a high etching rate selectivity of J, St and SiO2, and The cross section is vertical, there is little side etching, and the A
Ai's lewd sex; Kaku and Horu.

Furthermore, it goes without saying that by scanning a focused laser beam, it is possible to etch a wide sample area with high laser power.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

(Example 1) FIG. 4 shows a first embodiment of the present invention. St.

A sample 41 of 5lO2 is transferred from the gas introduction pipe 42 to the vacuum device 4.
It is placed in an atmosphere of chlorine gas or fluorine gas 43 introduced into the atmosphere. The sample 41 is irradiated with a laser beam 45 emitted from an Eyashimer laser 44 through a window 46. As the excimer laser 44, a XeCL excimer laser or a U XeF excimer laser is used when chlorine gas is used, and a XeBr excimer laser is used when fluorine gas is used. By irradiating the laser beam 45, the chlorine gas or fluorine gas 43 becomes an activated etching species 47, and at the same time, the electronic state of Si on the sample 41 is excited, so the Si in the portion irradiated with the laser beam 45 is Only the laser beam is etched with a high etching rate, and the laser beam is Glt.

5IO2 is difficult to be etched. In this way, by irradiating the sample 41 being etched with the ion beam 49 from the ion source 48 at low acceleration energy,
It is possible to help the etching progress anisotropically, and the etched cross section of the sample after etching is vertical, and side etching under the mask is hardly observed. Furthermore, by appropriately selecting the output of the laser beam and lowering the acceleration energy of the ion beam, damage caused by laser beam irradiation and ion bombardment created on the laser beam and ion beam irradiated surface of the sample 41 during etching can be reduced. It becomes less.

(Example 2) FIG. 5 shows a second embodiment of the invention. St.

A sample 51 of 5IO2 is passed from a gas introduction pipe 52 to a vacuum device 5.
It is placed in an atmosphere of chlorine gas or fluorine gas 53 introduced into the atmosphere. As the excimer laser 54, a XeCt excimer laser or a XeF excimer laser is used when chlorine gas is used, and a XeBr excimer laser is used when fluorine gas is used. The chlorine gas or fluorine gas is activated by the laser beam 55 irradiation, the electronic state of St is excited, and only the Sl on the laser beam irradiated surface is etched at a high etching rate. In this embodiment, the laser beam 55 to be irradiated is sufficiently focused, reflected by a reflecting mirror 510, and then irradiated onto the sample 51. The reflecting mirror 510 has a structure that allows its solid azimuth to be continuously changed mechanically, and by controlling the change in the azimuth of this reflecting mirror 510, it is possible to directly target any minute area using a focused laser beam. Etching can be performed. In addition, by scanning a focused laser beam using similar control,
It is also possible to etch large areas with high laser power. Furthermore, by irradiating the sample 51 during etching with the ion beam 59 from the ion source 58 at low acceleration energy, it is possible to perform etching with a vertical etching cross section and less damage caused by ion bombardment. be.

〔Effect of the invention〕

The etching rate selectivity of Si, 5t02 by the etching method of the present invention and the etching rate selectivity by the conventional ion beam etching method without laser beam irradiation are shown in FIGS. 6 and 7.

The horizontal axis in FIG. 6 is the partial pressure of chlorine in the vacuum apparatus, and the vertical axis is the ratio R(
S l )7'R(S r 02 ). 61,6
In both cases 2.63 and 8.63, argon gas is flowed into the ion source in vacuum to increase the pressure of the vacuum device. OX 10 To
It is set as rr. According to the method of the present invention, 61 further introduces chlorine gas from the gas inlet tube into the vacuum apparatus having an argon atmosphere, and performs etching by irradiating the sample with a XeCL excimer laser all at once in the chlorine gas atmosphere, and at the same time accelerates the etching by 50 eV. This is the etching rate selectivity when ion beam irradiation is performed at 62 is obtained by the method of the present invention,
This is the etching rate selection ratio when a sample is irradiated with a XeF excimer laser and a batch irradiation beam in a chlorine gas atmosphere under the same conditions as in No. 61. No. 63 uses the conventional method to further introduce chlorine gas from a gas introduction tube into a vacuum apparatus with an argon atmosphere, and to generate a voltage of 1 keV in the chlorine gas atmosphere.
Etching rate selection ratio when ion beam etching is performed with acceleration, and laser beam irradiation is not performed. From the comparison of 61, 62, and 63, the laser beam etching using ion beam irradiation in a chlorine atmosphere according to the present invention shown in 61 and 62 is superior to the ion beam etching in a chlorine atmosphere using the conventional method shown in 63. yo, D also has an error 1-tugrate large as s-b'=,
It can be seen that the effect of laser beam irradiation according to the present invention is extremely large.

FIG. 7 shows the etching rate selectivity when etching is performed using a XeBr excimer laser in a fluorine atmosphere. The horizontal axis in FIG. 7 is the fluorine partial pressure in the vacuum apparatus, and the vertical axis is the etching rate ratio R (8
1)/R(sto2). 71.72 In both cases, argon gas is flowed inside the ion source in vacuum, -
r blind f19 W iFI's flute power or just n Xi n-”
Tnrr)-l layer. According to the method of the present invention, fluorine gas is further introduced from the gas introduction tube into the vacuum apparatus having an argon atmosphere, and the sample is irradiated with a XeBr excimer laser at once in the fluorine gas atmosphere to perform etching. This is the etching rate selectivity when ion beam irradiation is performed at an acceleration of 50 eV. 72 is
According to the conventional method, fluorine gas is further introduced from a gas introduction tube into a vacuum apparatus with an argon atmosphere, and the laser beam is No irradiation was performed.

From a comparison between 71 and 72, it is found that the ion beam etching combined with ion beam irradiation in a fluorine atmosphere according to the present invention shown in 71 is superior to the ion beam etching in a fluorine atmosphere by the conventional method shown in 72. It can be seen that the etching rate is much higher, and the effect of laser beam irradiation according to the present invention is much greater.

Furthermore, in the laser beam etching using 61.62 and 71 ion beam irradiation according to the present invention, ion beam irradiation is also used, although the acceleration energy is low, so the high acceleration energy of 63.72 using the conventional method is As in the case of ion beam etching, the etching cross section was vertical, and there was some side etching under the mask.

In addition, in the cases of 61, 62 and 71 according to the present invention, the ion acceleration energy is lower than in the cases of 63 and 72 according to the conventional method, so damage caused by ion bombardment on the ion irradiated surface is extremely small, and the effect of the present invention is It was obvious.

According to the above detailed communication, according to the present invention, 810 □ of St.
It is possible to increase the etching rate selectivity for
Furthermore, it is possible to perform etching with a vertical etching cross section and less damage caused by ion bombardment. Moreover, by condensing laser irradiation, it becomes possible to directly etch any fine area with a good etching rate selectivity. If the present invention is used in a dry process for manufacturing electronic devices, it will be extremely effective.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the wavelength distribution of the absorption coefficient of chlorine and fluorine and the laser output wavelength, Figure 2 is a diagram showing the wavelength distribution of the absorption coefficient of Si and the output wavelength of the laser, and Figure 3 is a diagram showing the wavelength distribution of the absorption coefficient of Si and the output wavelength of the laser.
FIG. 4 is a cross-sectional view of a vacuum apparatus showing a first embodiment using the etching method of the present invention, and FIG. 5 is a diagram showing the wavelength distribution of the transmittance of tO2. 6 and 7 are diagrams comparing the etching rate selection ratio of Si, 5in2 according to the present invention with the etching rate selection ratio according to the conventional method. . 40.50... Vacuum device, 41.51... Sample, 4
2.52...Gas introduction pipe, 43.53...Chlorine molecule or Huff-X molecule, 44.54...Excimer laser-1
45,55... Laser beam, 46.56... Window, 47.57... Activated etching species, 48°5
8...Ion portion, 49.59...Ion beam, 5
10... Child verse I0゛1 River Province M anti-body 4 memories. Figure 1 Wavelength (Sleep Figure 2 Wavelength (n skin) Figure 3 Wavelength (rL turtle)

Claims (1)

[Claims] (1) Irradiate St in a fluorine gas atmosphere or a chlorine gas atmosphere with a XeBr excimer laser, a XecL excimer laser, and a XeF excimer laser,
A laser beam etching method characterized by simultaneous ion beam irradiation and etching.