JPS60165725A - Dry etching method - Google Patents

Abstract

PURPOSE:To etch a sample in an anisotropic manner by supplying reactive gas which contains halogen element and film forming gas to a vessel which contains a sample, vertically emitting selectively a light for ionizing the reactive gas. CONSTITUTION:P-added polysilicon 33 is superposed through a SiO2 film 32 on an Si substrate 31, a sample 12 coated with a resist mask 34 is disposed in a vacuum chamber 11, and Cl2 and Si(CH3)4 are supplied. An ultraviolet rays 17 having 300-400nm of wavelength is emitted, a polysilicon 33 is etched with produced Cl radical, and a thin film 35 of Si(CH3)2Cl2 is accumulated. The accumulating reaction and the etching reaction compete, thereby performing an anisotropic etching without an undercut. The sample is a semiconductor material, a high melting point metal or its silicide, and the mask may be separaely formed. The film forming gas employs organic metallic compound such as organic silane, organic Ge or its halogen derivatives or silane phosphine. According to this method, the anisotropic etching can be performed without irradiation damage.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to anisotropic dry etching technology using photochemical reactions.

[Technical frequency and problems of the invention]

In recent years, integrated circuits have been increasingly miniaturized, and prototypes such as SIs with small pattern dimensions exceeding 1 to 2 [μm] have recently been developed. Plasma etching technology is essential for such microfabrication. Brassuma ■ Tubungu technique 1
60 As one example, a parallel deck electrician (C in a container with Φ)
"When a reactive gas such as F4 is introduced," 13.56
A sample is placed on an electrode (cathode) to which high-frequency power of [Ml-1z] is applied, and a glow discharge is generated between each electrode to generate plasma, and a negative I! There is a method in which positive (-A) in the plasma is accelerated by the cathode drop voltage generated on i, and the sample is bombarded with C etching.This method is called reaction 1!!-1'A etching (RIE ), it is currently the mainstream of microfabrication technology.

However, in this type of method, since the sample is placed in plasma, the oxide film is destroyed due to the charging of charged particles such as ions and electrons, and the threshold value due to soft X-rays. In addition to inducing voltage shift 1 to 1 in the oxide film, various radiation damages such as metal staining from the inner wall of the chiton board were caused.

These radiation damages can be caused by ultra-L
There are many factors that can be fatal to SI,
Therefore, there is a strong need for a damage-free etching technique that does not cause radiation damage.

As a damage-free dry etching technique, anisotropic etching (for example, t-1, Akiya etching) using an atomic F beam whose kinetic energy is only equal to the gas temperature during glow discharge has recently been used.

proo, 3rd, 3ymp, On Dry
processes, ρ119 (1981)), etching using a laser or ultraviolet light (e.g., T,
J, 01ltlan (+: J, chei,
ptrys.

74, 1453 (1981): H, 0kano,
T, Yalazakl.

M, 5ekine and Y, Horlike,
proc, of 4 tl+symp, on l
”)ry p+ocesses, P6 (1982
) etc. have shown the possibility of damage-free anisotropic etching.

, J, /-14< ffeAccording to the research by Akishiya et al., I-
1a-X e-C due to the front side of the ultraviolet rays emitted by the under
In poly-Si etching in I2 atmosphere, conventionally reported ion-assisted etching (e.g. 1, IW, ('', obburn and l-1,
F., Winters, J.

Δ1 hit l, I+hyS,! io, 31H (19
79)) similar effects were found (e.g., H,
Okano, T.

Yamazaki, M., 5ekine and
'/, l-10riike.

proc, of 4 mouth 1 3 ymp, onD r
V 1) rOCesses, P 6 (1982)). In other words, there is an effect that the etching reaction on the light-irradiated surface is significantly accelerated compared to the non-irradiated surface. However, for example, phosphorus is added at a high concentration [) + poly Si, MO, W, Ta, or its silicone! : The same was observed in the compound.

However, this type of method had the following problems. That is, due to the entry of reactive gas radicals photodissociated in the gas phase under the mask and the slight scattered light from the surface to be etched, an undercut 2 is produced under the etching mask 1 as shown in FIG. That's true. This undercut 1-2 becomes a major factor that hinders the miniaturization of elements, and is a fatal drawback in ultra-LSIs. In addition, 31. VcFl to be etched such as L poly 81, 4
5 indicates an IO2 film, and 5 indicates a Si substrate.

[Purpose of the invention]

The object of the present invention is to be able to achieve anisotropic etching without causing any irradiation loss to the specimen to be etched,
The object of the present invention is to provide a dry etching method that can contribute to miniaturization and higher integration of semiconductor devices.

[Summary of the invention]

The gist of the present invention is to form, eg, deposit a film on the exposed surface of the sample during etching of the sample to be etched, and to achieve anisotropic etching by utilizing competitive reactions between these etchings and film formation.

-〇- That is, the present invention is a method of etching a sample to be etched by photochemical reaction.
U le+! Dry etching h
I3 in lA, said i! A reactive gas containing a halogen element and a gas to be used for film formation are introduced into a reaction vessel containing a halogen element, and the above reactive gas is dissolved.
1f? Light is guided into the container, and this light is applied only to the parts of the first two samples that are to be etched.
This method involves direct irradiation.

(Effect of brightening) In the present invention, if J:, electrons, etc., charged particles such as ions are
(Put the sample to be etched under the light beam 141 without
- Able to tutchinku. Therefore, it is possible to eliminate radiation damage, which is extremely effective for semiconductor device manufacturing. Furthermore, the competitive long window between etching and film formation enables anisotropic etching, which contributes to miniaturization and higher integration of semiconductor devices.

[Embodiments of the invention]

FIG. 2 is a schematic diagram showing a dry etching apparatus used in an embodiment of the present invention. In the figure, 11 is a vacuum container (reaction container) that forms an etching chamber, and this container 11
A slat 13 on which a sample 12 to be etched is placed is placed inside. In addition, the container 11 contains reactive gas and J
A gas inlet 14 for introducing gas for ft volume and a gas 131 air port 15 for exhausting the inside of the container 11 are provided.
Being beaten. Then, a mixed gas of a reactive gas containing a halogen element such as CI2 and a deposition gas consisting of, for example, four molecules of Si (CH3) is introduced into the container 11 through the gas inlet 14. 1 is there.

On the other hand, a light source 16 is arranged at the top of the container 11 to dissociate the reactive gas. This light source 16 is
For example, it is an excimer laser whose emission center is at a wavelength of 308 nm. The light 17 from the light 8!16 is vertically irradiated onto the upper surface of the sample 12 of the sahipta 13-1- through an ultraviolet light passing window 18 provided in one wall of the container 11. 1 causes the reactive gas to be dissociated.

For example, when using CI2 as the reactive gas, CI2
Because it absorbs light in the vicinity of 330 [nml], it is activated with extremely high quantum efficiency by irradiation with this light! l', '=
'KCl radicals are generated. However, test F112 is designed to be irradiated with two light beams [16 to J:] all at once.

When etching phosphorus-doped poly-Si using such an apparatus, C12 is used as a reactive gas, 5i (CH:l)4 is used as a deposition gas, and the laser described above is used as a light source 16. As mentioned above, the CI in the optical path due to light irradiation
The two molecules emit active C1 atoms and etch phosphorus-added poly 81 and the like.

At the same time, this active C1 atom is Si(CH3)4
For example, 5i(CI-(9)2CI2
Generates a 7-summer like . Figure 3 shows the deposition rate of such monomers and the deposition rate of phosphorus-doped poly-Si.
It shows which relationship.

In the figure, the ○ mark indicates the etching rate of poly 3i, and the * mark indicates the Jft f# rate of the monomer. Note that the above etching speed and j11 lamination speed are based on the etching rate when the mask 21 is etched when the phosphorus-added poly 5112 on which the etching mask 21 is formed as shown in FIG. 4 is etched using the apparatus shown in FIG. 511 of the existential E part
-C shows the etching rate of 2 and the Jfi product rate of /mar of mask 21-1, respectively. From Figure 3, the monomer's stacking velocity is CI 2 i-31 (CH3)
The total pressure of 4 is 10 [1'0rrl or more 1. - Jj
It can be seen that the number of cases increases rapidly. On the other hand, the etching rate of polySt increases with increasing total pressure;
It shows the maximum value at a pressure of about [torr], and as the pressure increases further, the etching speed 11 suddenly decreases (i(-F). The reason for this is the following.

That is, the monomer deposited on the poly 811 is removed by etching the poly S1, but since the deposition rate II of the poly 811 is high where the pressure is high, the etching of the poly S1 is affected accordingly. Conceivable. Furthermore, it was found that when 5i(Cf-13)4 was added to CI2, the etching speed increased by about 211i! degrees compared to the etching speed of CI2 (J). [As a result of investigating the shape of phosphorus-added poly S1 in terms of torrl, it was found that at 1 [torr], it was seven torr.
Since the tl product is very small, a large undercut is recommended, and at 100 [torr], the monomer's tl is very small.
``It is desirable to obtain a shape with a very good product, but 3 Q
An anisotropic shape without undercut was achieved at [torr].

Next, an etching method using the above apparatus will be explained.

As the sample 12 to be etched, phosphorus-added poly S1 was used. That is, as shown in FIG. 5(a), the phosphorus-added poly Sl l! (Test FI to be etched) A film was used in which a film 33 was deposited and an etching mask 34 made of resist or the like was formed on the film. Cl2 was used as the reactive gas, and Si (CH:I)4 was used as the loading gas.The light 17 from the light source 16 was ultraviolet light with a wavelength of 300=-/I00 [nm]. Toshita.

nζ1 Container] The sample shown in FIG. 5(a) was placed in the container 1, and a reactive gas and a deposition gas were introduced into the container 11, and ultraviolet light was introduced into the container 11.

The reactive gas introduced into the container 11, that is, CI2, is dissociated by irradiation with light to generate C1 rad/l. These C1 radicals etch the poly-Si film 33 as the sample to be etched. On the other hand, the 1" loading gas, that is, Si(CH3)4, introduced into the container 11 reacts with the dissociated C1 radicals, resulting in Si(CI-IEI)2
G 12 and other monomers are produced. Here, the above-mentioned monomer forms a new thin film (deposition m) on the surface of the poly S1 film 33 and the mask 34.This Iff product reaction and the lateral entry of C1 radicals, which are nipyanants, and the reflected light cause The etching reaction on the sidewalls of the pattern competes with the etching reaction, which prevents an increase in undercut.On the other hand, on the light irradiated surface, the etching reaction progresses with the 11 product reaction due to the photo-assisted effect. Vertical etching proceeds, resulting in anisotropic etching without undercuts.

Figure 5(b) shows the poly 5i113 sample to be etched.
3 is etched halfway. In this case, since the mask 34 is not etched with 01 radicals, the L sumers 35 or j' are deposited on the mask 34. Furthermore, since the etching side wall 3G is not irradiated with light, the monomers 35 are deposited as well. On the other hand, on the poly 5133 where the mask 34 does not exist, the etching precedes the monomer deposition, so the 7-layer film is not deposited.In other words, the deposited film on the light irradiated surface is quickly etched and the poly 5133 is etched. Etching progresses.

On the side wall which is not irradiated with -1, ), the Jri product reaction is faster than the etching, so the ultra-thin 1" laminated film 35 remains and protects the side wall, thereby achieving J: anisotropy. By continuing this etching, the poly 5i33 will be cut into the shape shown in Figure 5 (C). H
(The fA film 35 is extremely thin on the etching sidewall 3G, and there is almost no problem such as a decrease in pattern accuracy due to this film thickness.

Thus, according to this embodiment, it is possible to effectively etch the phosphorus-doped poly S1 film 33 as a sample to be etched by light irradiation without using irradiation damage without using charged particles such as electrons or ions. can.

In addition, due to competitive reactions such as etching with reactive gas and light and deposition with jet stacking gas, the poly 3i11 is formed while forming a thin III layer 35 on the etching sidewall.
33 can be etched vertically. In other words, it is possible to achieve anisotropic etching, which is extremely effective for microfabrication, and has great effects on miniaturization and high integration of semiconductor devices. Further, since the deposition gas can be indirectly dissociated only by using light for dissociating the reactive gas such as CI2, there is an advantage that only one light source is required.

Note that the present invention is not limited to the embodiments described above. For example, as shown in FIG. 6, the light irradiation method may use a rectangular beam that is longer than the major axis of the sample 12 to be etched, and scan the sample 12 uniformly with this beam. Furthermore, as shown in FIG. 7, the entire sample may be etched using a small-diameter rectangular beam while sequentially moving the etchant-generated tIAbX using a step-and-living method. Further, the mask for the selective etching is not limited to a resist pattern formed directly on the sample to be etched, but a mask material 42 formed on a quartz substrate 711 as shown in FIG.
It is also possible to use a mask substrate to which a mask is selectively attached, and to irradiate the sample with light from above the mask through the mask while the substrate is separated from the sample. In this case, the deposited film is also deposited on areas not exposed to light, but since this film is easily dissolved in an organic solvent such as acetone, it can be removed by a simple post-treatment after etching. .

In addition, the sample to be etched is not limited to poly 3i, but also A
It can be applied to high melting point metals such as I, A1 alloys, Ta, W, and Mo, silicide compounds thereof, and other semiconductors. Further, the reactive gas is not limited to C12, and may be a gas containing a halogen element such as fluorine or bromine, or a gas containing carbon, boron, hydrogen, or the like in these. Furthermore, the deposition gas was 81 (CI-13
) 4, but is not limited to organic silanes, organic germaniums, organic aluminums, organic galliums,
Organometallic compounds such as organophosphines, organoboranes, organoarsines, especially alkyl organometallic compounds,
Alternatively, the halogen 1 may be a conductor, or may be silane, phosphorus, arsine, etc., as long as it contains at least one of a semiconductor or a metal and at least one of carbon or hydrogen. Further, instead of the 1M volume gas, it is also possible to use a gas that reacts with the sample to be etched to form, for example, an oxide film.

Further, the wavelength of the light may be appropriately determined depending on the type of reactive gas to be dissociated. Furthermore, the light source is not limited to one that generates coherent light such as a laser;
It may also be a device that generates incoherent light, such as a Xe lamp. In addition, without departing from the gist of the present invention,
Various modifications can be made.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining the problems of the conventional method, FIG. 2 is a schematic configuration diagram showing a dryer and etching apparatus used in an embodiment of the present invention, and FIG.
1. Characteristic diagram showing the relationship between etching rate and monomer deposition rate. Figure 4 is a cross-sectional view of the sample used to measure the above relationship. Figures 5 (a) to (C) are graphs showing the relationship between the etching rate and the monomer deposition rate. FIGS. 6 to 8 are a perspective view and a sectional view, respectively, for explaining modified examples. 11... Vacuum container (reaction container), 12... Sample, 1
3... Susceptor, 14... Gas inlet, 15...
Gas exhaust port, 16 light source, 17...light, 18...ultraviolet light passing window, 31...811 plate, 32...5iO21
1, 33... Phosphorus-added poly S1 (sample to be etched), 34 Etching mask, 35... Monomer (deposited film), 41... Quartz plate, 42... Mask material. Applicant's agent Patent attorney Takehiko Suzue 17- Figure 1, Figure 2

Claims (7)

[Claims] (1) In a dry etching method in which a sample to be etched is selectively etched by a photochemical reaction, a reactive gas containing at least a halogen element and a gas used for film formation are introduced into a container containing the sample; A dry etching method characterized in that a portion of the sample to be etched is selectively irradiated with light that dissociates a reactive gas and perpendicularly to the sample. (2) The dry gas according to claim 1, characterized in that the gas used in the step 11 (11) for forming the film contains at least one of a semiconductor or a metal, and at least one of carbon or hydrogen. Etching method. (3) The gas used for the film formation is an organic silane, an organic germanium, or an organic aluminum. Organic galliums, organic flusphins, organic boranes,
Claim 1 or 2, characterized in that the compound is an organometallic compound such as organic arsine, or a halogen derivative thereof, or silane, ph4sphine, arsine, etc.
Dry etching method described in section. (4) The means for selectively irradiating the light is C, a mask is formed on the sample in advance, and the light is irradiated onto the sample from above the mask. Dry etching method described. (5) A patent characterized in that, as means for applying the light before selecting l)1, a mask is placed on the sample at a distance from the sample, and the sample is irradiated with light through this mask. A dry etching method according to claim 1. (6) The dry etching method according to claim 1, wherein the light is coherent or incoherent light. (7) The sample to be etched is a semiconductor material, a melting point metal, or a silicide compound thereof.
*The etching method according to claim 1.