JPS58100683A - Plasma etching method - Google Patents

Abstract

PURPOSE:To prevent silicon from being undercut during etching with gas plasma and to attain an enhanced yield by using a gaseous mixture contg. a prescribed amount of H2 and >=1 kind of gas such as CCl4, CCl3F or CCl2F2. CONSTITUTION:Silicon 6 is mounted on a smaple electrode 2 in a reaction chamber 1, and the chamber 1 is evacuated. A small amount of a reactive gas contg. 15-50% H2 and >=1 kind of gas selected from CCl4, CCl3F, CCl2F2, CClF3 and CF4 is fed into the chamber 1. It is then exhausted to maintain the chamber 1 at a certain vacuum degree. By applying a high frequency voltage between the electrode 2 and a counter electrode 3 facing to the electrode 2, the silicon 6 is etched. By this method the etched pattern of the silicon undergoes no undercutting, and an enhanced yield is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma etching method capable of microfabrication of polycrystalline silicon using plasma of a reactive gas generated by high-frequency discharge. As a method, a plasma etching method using a plasma tube using high-frequency glow discharge of Freon gas or the like has become widely used.

CCZ. is used for plasma etching of polycrystalline silicon. .

CCLBF, C French F*, cczy. , C.F.
4 (D L 5 'l Casb" is often used 0 The biggest problem with etching with these gases is undercut 0 The degree of undercut depends on etching conditions such as degree of vacuum, etching gas species, polycrystal 0 example i;I'CF.10C/,F which varies depending on the silicon material
In the case of s, an undercut of the same degree or more as the film thickness of polycrystalline silicon occurs regardless of the material of the polycrystalline silicon.
CCt4lCCtsF, CCt*F doublet B, CF4
(!: CCLFH ノ14 Combined K Comparatively, the degree of uncut [2 is small0. The more vacuum there is, the smaller the undercut tends to be. However, in the conventional method using such a gas, in the best case, a polycrystalline silicon film with a thickness of 0.5 μm is etched and the undercut is reduced to 0.5 μm. It was difficult to suppress the height to 17 m or less.

On the other hand, semiconductor-integrated oil passages require increasingly finer battens, and therefore requirements for undercuts are also becoming stricter.For example, pattern m0.
It is thought that a demand for an undercut amount of 0 to 05 pvpt or less at 7 to 0.8 μm will definitely arise in the near future. Therefore, determining how to reduce the undercut is extremely expensive for etching technology.However, the above-mentioned drawbacks of the conventional technology are fatal to the etching process in the production of semiconductor integrated circuit devices. It can be said that it is a thing.

In order to solve these drawbacks, the present invention provides the reaction casts L, CCt4, Cct, F', CCttF
Provided is a plasma etching method that maintains an excessive etching rate for polycrystalline silicon and does not cause side etching by using a mixed gas containing at least one of m, CCJFm, and CF and containing H3t. It is something to do.

In order to achieve the above object, the present invention is characterized in that the etching chamber is equipped with a sample 11L electrode on which the sample to be etched is placed and a counter electrode that faces the sample electrode, and is exhausted while flowing a reactive gas into the etching chamber. In the method of etching the sample to be etched using gas plasma generated by applying a high frequency voltage to both the electrodes while keeping the chamber at a vacuum level within a certain range, the reaction sludge h < TOMOCC1.
,,CC11F, CC1,F,.

Using a mixed gas containing at least one of CCtF and CF4 and containing Hl, Ht in the mixed gas is
The purpose of the invention is to provide a plasma etching method characterized in that a gas containing 15 to 50% of the amount of etching is used.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments are merely illustrative, and it goes without saying that all modifications and improvements may be made without departing from the spirit of the present invention.

Figure @1 is an example of a cross-sectional view of a plasma etching apparatus used in the present invention. In the figure, 1 is a reaction chamber, 2 and 3 are sample electrodes and counter electrodes installed in parallel to each other in the reaction chamber, and 4 is a gas attached to the sample electrode 2 that introduces the reaction gas for etching between the two electrodes. An inlet pipe 5 is attached to the reaction chamber 1 and a gas exhaust pipe is used to exhaust the gas inside the reaction chamber to the outside; 6 is a material to be etched placed on the sample electrode 2; and 7 is connected to both electrodes. This is a high frequency power source for generating plasma of reaction gas for etching. In addition,
The spacing between the two electrodes is generally 2 to 10 mm. To etch the material to be etched 6 using a plasma etching apparatus configured in this way, a reaction gas is introduced into the reaction chamber and the gas is evacuated using a vacuum pump. While maintaining the degree of vacuum in the reaction chamber 110-3 to several Torr by exhausting from the tube 5, a voltage of several 100 V to several KV is applied between both vjL ports, 13
．． A high-frequency voltage of 56 MHz is applied to generate one lasma by high-frequency glow discharge. The active chemical species present in this plasma react with the material to be etched, such as single crystal silicon or polycrystalline silicon, to generate volatile compound noise, which is exhausted and removed from the etching chamber through the exhaust pipe 5, thereby causing etching. progresses.

The plasma etching method of the present invention will be explained in detail with reference to Examples below.0 A material to be etched 6 is placed on a sample electrode 2 in a reaction chamber,
After the reaction chamber is evacuated using a vacuum pump and the degree of vacuum becomes sufficiently low, gas 5, for example CC4Rk 50 SCCM, is introduced from the gas introduction pipe 4 as an etching reaction gas.

H, t-25SCCM was introduced, and the degree of vacuum in the reaction chamber was reduced to 0.
Maintain at 18Torr o 400W (13,56MH
AJ+TL wave power of z ) is applied between both electrodes and s CC
A plasma of 1 Jt and H3 mixed gas is generated to perform all etching. When etched under these conditions, the etch rate of the Aa-doped polycrystalline silicon film as the material to be etched 6 was 540^/min. Photoresist AZ-1 commonly used as etching mask material
The etching rate for 370 (trade name manufactured by Silaplay Corporation) was 170^/min.0 Also, when the batten 1liI'r surface of the h-doped polycrystalline silicon film was observed with a scanning electron microscope, undercuts were observed. is 0.05μ
m or less.

For example, in the manufacturing process of a circuit for a silicon gate MO8 series 8, silicon dioxide is formed on a silicon substrate to become a gate i-oxide film, and then silicon dioxide is formed to become a gate silicon film.
Form a doped polycrystalline silicon film. When an M-doped polycrystalline silicon layer having such a structure is selectively etched using a resist t mask, an appropriate etch rate is obtained.

It is required that there is no undercut in the etching gas. In the above embodiment, when the thickness of the M-doped polycrystalline silicon film is i 5000 A, the etching time is about w minutes, which can be said to be an excessive value from the viewpoint of practicality and controllability. Further, since the undercut of the etching button is 0.05 μm or less, microfabrication with much higher precision than conventional methods can be easily carried out.

CC4, CC41F *CC for etching reaction gas
Although the details of why no undercut occurs in the material to be etched 6 when using 4F* eCctFs or a mixed gas of CF4 and nitride are not clear,
The following words are inferred: o CC1*, cczl
F, CC14Ft.

In the glow discharge plasma of CCLF, or a mixed gas of CF and Ha, the etching reaction is mainly caused by chlorine ions, radicals, fluorine radicals, etc.
A plasma polymerization reaction occurs in which the main factors are carbon atoms dissociated from F, 6, OF, etc., and atoms in water 3.

Since the etching reaction and the plasma polymerization reaction are carried out in parallel on the surface of the material to be etched 60, plasma polymers adhere to the resist 1 and the side walls of the doped polycrystalline silicon film as the etching progresses. Lateral etching is prevented by polymer particles adhering to the side walls of the etching button, but on the plane parallel to the substrate surface, polymer growth is inhibited by ions incident perpendicularly to the substrate surface. According to this example, the material to be etched after plasma etching was observed with a scanning electron scanning mirror, and a thin film of the polymer was observed on the am of the As-doped polycrystalline silicon film. It was confirmed that it was attached.

Figure 2 shows the etch rate of M-doped polycrystalline silicon (indicated by broken line A) and the amount of undercut (broken line
(indicated by MB). The etching conditions at this time were: RF Kamikata force: 400 W, pressure: 0.18 T.
orr- foot. In the case of CCZ-F alone, the VC shows a relatively large etch rate of 770 A/min, and the undercut amount also shows a value of 0.16 Pm for a film thickness of 0.5 μm, which is a little more than about 31111. On the other hand, C bribe F.

When H snow is mixed in, the etch rate is 520 to 500 A/min when the mixing amount is 15 to 50X, and the undercut amount is reduced to 0.06 to 0.02 pm.

Even if Htt is mixed in this way, it is practical and has the ability to perform etching with good controllability because it has an appropriate etch rate, and it is possible to form an etching pattern with no undercuts. . In addition.

Although it is not shown in the figure, if the low temperature amount of H exceeds 5ON, it is not practical because the etch rate decreases rapidly. In addition, if the amount of resin mixed in is less than 15X, the effect of suppressing undercut is reduced.

Figures 1 and 2 show examples of As-doped polycrystalline silicon films, and examples of polycrystalline silicon films doped with other impurities such as P-doped polycrystalline silicon and polycrystalline silicon films doped with no impurities. A similar tendency is shown for materials to be etched such as etching gases.Although this example shows only CC4Fm as an etching gas, the present invention uses a method in which KHz is mixed in to actively utilize plasma polymerization as described above. . Therefore, H Goose is mixed in lj Ska CC1+
+ CC14Ft disturbance CC14Ft v CCtFl
, CF4 noise or mixtures thereof, Mayu, them and other N.

Even if the gas is mixed with 10M, by controlling the amount of H8 mixed in to tm, plasma polymerization can occur and undercut can be prevented. However, the present invention is not limited to CC4F.

As explained above, the present invention uses CC in the etching reaction gas.
t4. CCtaF, C false F, , CC/, Fl
and Ck-, and H! By using a mixed gas containing , there is no undercut in the etching pattern of polycrystalline silicon, and it is practical.

Since it is possible to maintain a well-controlled etch rate, it is highly effective in the etching process in semiconductor device manufacturing.
This contributes to improving v.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of the plasma etching apparatus used in the present invention, and FIG. 2 shows the plasma etching process performed by plasma discharge of a mixed gas of CC4Ft and H according to the present invention. This figure shows the relationship between the etch rate and the amount of undercut with respect to the amount of Ht mixed in when As-doped polycrystalline silicon 11 is etched. In the figure, etch rate %B indicates the amount of undercut. 1... Reaction chamber, 2... Sample electrode, 3...
...Counter electrode, 4...Gas introduction tube, 5.
... Gas exhaust pipe, 6 ... Material to be etched, 7 ... High rope wave power source patent applicant: Nippon Koshin Telephone Corporation

Claims (1)

[Claims] An etching chamber equipped with a sample electrode on which a sample to be etched is placed and a counter electrode facing the sample electrode is evacuated while a reaction gas is introduced into the etching chamber to maintain a degree of vacuum within a certain range. In the method of etching the sample to be etched using a gas plasma generated by applying a full high frequency voltage to both electrodes while maintaining the etching temperature, the reaction gas includes at least CC1. CC1aF, Cc74F*-CC1Fsh and C
A mixed gas containing at least one of F4 and Hat' is used, and the amount of H8 mixed in the mixed gas is 15
50% plasma etching method.