JPS5928341A - Dry etching method - Google Patents

Abstract

PURPOSE:To prevent the production of any undercut at the time of any over- etching, by introducing a mixed gas of halogen gas and ozone gas when a reactive ion etching is applied by a glow discharge to a polycrystalline Si, high- melting metal or silicide compound mounted on one of opposing electrodes. CONSTITUTION:Opposing parallel plate electrodes 32, 33 are disposed in a chamber 31. The upper electrode 32 is grounded, while the lower electrode 33 is connected to a high-frequency power source 35 through a matching device 34. Further, the lower electrode 33 is supplied with a cooling water W and is provided thereon with a material 37 to be etched through an electrode member 36. As the material 36 to be etched, a polycrystalline Si 3 is employed which has an SiO2 film 1 on its surface and has been doped with P, and is provided thereon with a resist film 4 as a mask material. The halogen gas X2 with a regulated flow rate is introduced into the chamber 31 through a gas inlet 38a, and O3 as an addition gas generated in an ozonizer 40 is introduced into the chamber 31 through a gas inlet 38b, to perform etching by a glow discharge caused in the chamber 31.

Description

[Detailed description of the invention]

[Technical field to which the invention pertains] The present invention relates to a reactive electrolyte method (・ζ). [Prior art and its problems] In recent years, as the density and performance of semiconductor integrated circuits have increased, microfabrication has become more and more accurate. There is a strong demand for wet etching to be carried out in the past.
When wet etching is applied to the etched area, so-called undercuts are likely to occur, so there is a problem in that it is not possible to form a pattern with high shape accuracy. For this reason, it has an excellent strength of 10% and is highly reactive with the underlying material.
) is becoming the mainstream of etching processing technology. When etching PO6y-Si by reactive etching with CF, 1.3r, CF, , CC(1
Use a halogenated carbon gas such as No. 4. llIF5 Pogy-S i 3 as shown in Figure 1
In this case, by appropriately combining elemental halogen gases such as 1', 1', 11', and 11 gunified carbon,
It is possible to achieve undercut and directional etching. Here, 1 is an oxide film 72 is a half-layer, a body substrate, 4V
”, is a resist. However, as the density of water increases, the steps become steeper and a three-dimensional multilayer structure υ, side wall step part OJ P+)
Overetching is required when processing the 6-8 + 3 + 31 + 32 division method (Figure 2) or when processing a two-layer structure (Figure 3). Since machining accuracy is strongly required during Moeba etching, it is naturally essential that there be no undercuts. If the ionic reaction is strengthened in order to suppress the occurrence of undercuts, there is a drawback that the etching rate selectivity with respect to the underlying phase decreases. It is possible to obtain a high etching selectivity with respect to other materials to be etched without undercutting [7]. [Objective of the Invention] The present invention solves the above i'IC drawbacks by etching a reactive imager, that is, Pa(Jy-8+) by IE.
An object of the present invention is to provide a 17% directional etching method in which undercuts are 1r1c even when etching is performed. [Summary of the Invention] A mixed gas consisting of halogen gas and mason is supplied into an etching apparatus equipped with a blowfish 4J to be etched, plasma is generated in the atmosphere formed by the reactive gas, and plasma is generated in the plasma. The method is characterized in that the material to be etched is etched. In order to eliminate undercuts, even if the ionicity is strongly used, the undercut will be reduced to 1λ even if etching is performed, but on the other hand, even in regions with weak ionicity where there are many active radicals that cause undercuts, etching can be performed. Undercut may be reduced by selecting the gas appropriately. As shown in Fig. 4, during etching, etching products and etching residues become polymers and adhere to the etching side wall, and the undercut is stopped by 1M, and during anisotropic etching. It is presumed that The inventors of the present invention took into account the fact that n.
It was discovered that the etching target material on the etched side wall portion is coated with the above-mentioned redeposited material, and at the same time, 08 (ozone) is actively introduced to advance the oxidation reaction, thereby inhibiting the etching reaction on the side wall portion caused by active radicals. Ta. [Effect of the invention] By adding 0, (ozone) to halogen gas, 20
It has become clear that anisotropic etching without undercut can be easily achieved even with overetching of 0% or more. [Embodiments of the Invention] As for wave etching, a silicon substrate 2 is thermally oxidized as shown in the etched shape shown in FIG. -fI
fA (sio, ) 1, CV 1)
(Chemica6 Vaporde concave 5itio
Polysilicon 3 doped with phosphorus CP) deposited by the method n) was used, and a resist 4 was used as a mask material. Next, the apparatus used by the present inventors is shown in FIG. Q) r pump: 31 has 4 parallel plate electrodes facing each other 32
, 33 are crossed. Upper part? a, (32 is the contact J)
A high frequency power source 35 of 13,56 M Ilz is connected to the lower 'nv pole 33 via a stage adjuster 34, and cooling water W is flowed into the lower electrode 33. On the lower electrode is a polar moon 36 and a material to be etched 3 on top of it.
7 is placed. The reactive gas (X, ) is regulated to a predetermined flow rate by a flow rate regulator (not shown), and is introduced into the chamber 31 from the gas introduction D 38a. Also, ozone (Os)lr, which is an additive gas,
The gas inlet 38 is generated by the ozonizer 40 and distributed like halogen gas.
It is introduced into the chamber 31 from b. Excess dregs and reaction products in the chamber 31 are removed from the exhaust hole 39.
The air is exhausted through an exhaust system (not shown). ,
The material to be etched 37 is etched in a glow discharge generated in the chamber by applying high frequency power to the reactive ion etching device. Sa-CI''+fl rii: 9F as shown in Figure 7 When etching the polysilicon with the step structure j1°f shown in Figure 7 remaining (Figure 2; I), polysilicon 3 of l/sist 4] Etching has been completed, and 31 layers of polysilicon remain on the stepped portion of C.This etching remains II: '+
lj, it is necessary to remove 7 yote and remove it.''
I'm not even talented. Polysilicon film corresponding to the height of the stepped portion; 31
It is necessary to overetch until the polysilicon 32 is etched, and as shown in Figure 2 C, overetching can cause cracks in the polysilicon 32. . Similarly, as shown in Figure 3, when etching polysilicon 1 in the cell part of a two-layer structure, the second layer polysilicon 33 is substantially overetched, causing an undercut. The etching properties of 7F:r when using C1 reactive gas and [2C] alone and adding oxidation (011) are described below. high frequency power per electrode unit surface In 't 0.28 W/Crn
Apply 2 stamps and set the gas pressure to 0.11. The change in etching rate of phosphorous-doped polysilicon (Fig. 5a) and slo (Fig. 51)) with respect to ozone (o, ) In is shown.

[It's 7 things. When ozone M is added, the etching rate of polysilicon does not change up to 4 cc/lllIn i degree', but thereafter it decreases as ozone M increases. On the other hand, the etching rate for sio is extremely small, but it decreases compared to that for ozone. It is thought that the decrease in polysilicon egging rate as the aging of the polysilicon increases as the oxidation reaction of polysilicon gradually becomes more dominant. FIG. 6 is a graph showing the changes in the etching rate of undercuts on one side under the resist of a material to be etched with a film thickness of 1/Am of Lindor polysilicon. The etching conditions are similar to those shown in FIG. Figure 6a shows the case of Cet alone, undercant occurs with overegg, and with 100% overetch, 5
An undercut of 000X occurs, resulting in the shape shown in FIG. 2 C1 and FIG. 3, making it practically unusable. For it,
When 0.0 is added at 2 cc/min, as shown in Figure 6, no undercut occurs even when overetched by 100%. However, further d-bae googling will result in undercuts, and overetching by 200% will result in 700% overetching.
0 undercuts occur. Figure 2 3. Although it is satisfactory for etching the shape shown in FIG. 3, the three-layer structure requires overetching of 2()0% or more, which is still insufficient. However, 0. 4 cc/
When 1 nin is introduced, no undercut is observed even when etching is performed using a 25() chip as shown in FIG. 6C. Above, 0. It was revealed that by introducing this, undercuts can be prevented. If you introduce too much O8,
This is not preferable since polysilicon residue is likely to be formed on the 5-inch. [Other Embodiments of the Invention] The above embodiments took polysilicon as an example. . Exactly the same effect was observed with high melting point metals such as W and their silicide compounds.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the shape of polysilicon f-just coating using a resist as a mask without an undercut, and FIG. A cross-sectional view showing the conventional shape of polysilicon etching when
FIG. 3 is a cross-sectional view showing a conventional polysilicon shape with a two-layer cell structure, FIG. 4 is a cross-sectional view of a device used in an embodiment of the present invention, and FIG. Figure 6 is a characteristic diagram showing the relationship between 03 and etching speed using a -03 mixed gas, and Figure 6 is a characteristic diagram showing the relationship between undercut t[I and overetching due to the addition of 0.0% of the present invention.1...Oxide 3...Polysilicon 32
．． 33... Parallel flat plate fil: 45... High frequency power supply 37... Etched material 40... Mesonizer (7317) Representative Tanukito patent attorney Noriyuki Chika (and 1 others)
Name) Figure 1 Figure 2 L cL> Lm] 2nd
Figure (C) Figure 8 Figure 4 Figure 5 ρ/Z'3<2 5. <7, P
9 11r ozone 1 (007 minutes)

Claims (3)

[Claims] (1) Dry etching, which uses a mixed gas consisting of at least halogen gas and ozone gas to selectively and without undercut etching the material to be etched, which reacts with halogen, with respect to other materials. Method. (2) Has opposite electrodes that can apply high frequency power I7
, a glow discharge is generated by applying high-frequency power, and the above '
Scope No. 1 of Patent RII, which is characterized in that a mixed gas is introduced into a reactive ion etching device for etching a substrate to be etched placed on top of the RRT.
, <rt 11i1. dry etching method. (3) The first material to be etched is polysilicon and high melting point gold! 6 and these silylide compounds.