JPH03133125A - Resist ashing - Google Patents

Abstract

PURPOSE:To rapidly decompose a resist on a substrate for efficiently removing the same by a method wherein a gas containing fluoride is atmospheric- discharged to be jetted over the resist on the substrate heated or at the normal temperature. CONSTITUTION:After selectively etching and patterning an underneath film using a resist pattern as a mask, a silicon substrate 18 having a residual resist pattern is held on a substrate 3 in a quartz cell 1. Next, an opening and closing valve 15 of a gas feed pipe 13 on an ozonizer 14 side in closed; specific amount of CF4 is fed from a gas leading-in pipe 12 of a discharge tube 4 to a glass tube 8; the space between a mesh type electrode 9 and a winding electrode 10 is impressed with high voltage from a power supply 11 to atmospheric- discharge the CF4 gas fed to the glass tube 8 for exciting the electrodes 9, 10. Finally, the exciting gas is fed to the quartz cell 1 heated by a heater box 2 through another gas feed pipe 5 for ashing the resist pattern. Through these procedures, the resist on the substrate 18 can rapidly be decomposed to be efficiently removed.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to improvements in resist ashing methods.

(Prior Art) Conventionally, as a method of ashing a resist formed on a substrate, in 1972, GE's glue, A Ba1on
A method of ashing the resist by exposing the substrate to an ozone atmosphere or irradiating it with ultraviolet rays in an ozone atmosphere was developed by SC and OKung, and various improved methods have been proposed since then. For example, Tokuko Sho 64-4024
200 to 300 in an atmosphere of O2 and 820 gas.
A method of ashing a resist on a substrate by irradiating the resist with ultraviolet light of 260 to 210 tv is disclosed. In addition, Japanese Patent Application Laid-Open No. 63-2138825 discloses that 175 nm, 194 nm in an oxygen-containing atmosphere containing ozone
An ashing method is disclosed in which a resist on a substrate heated to 100 to 200° C. is irradiated with ultraviolet rays of 254 rv and the ultraviolet irradiance on the resist surface is defined to be 50 mW/cm” or more.

By the way, the decomposition rate of the resist in the above-mentioned ashing method requires several minutes for a film thickness of 1 μm. Furthermore, if the illuminance of ultraviolet rays on the resist surface, the substrate temperature, and the O1 concentration are increased, an ashing rate of about 1 μm/sin can be obtained depending on the conditions. However, increasing the illuminance of ultraviolet rays and heating temperature have problems such as damage to elements pre-formed on the substrate (especially semiconductor substrates) and oxidation due to ozone, so it is natural to increase the ashing rate by controlling these conditions. There is a limit. In addition, in the semiconductor manufacturing process, resists are exposed to plasma, various active gases, ions, etc. For example, phenol novolak resists undergo crosslinking, resulting in three-dimensionality and changes in chemical structure. The conventional ashing method of irradiating ultraviolet rays has the problem of not being able to ash at a sufficiently high rate.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and it is possible to quickly decompose the resist on the substrate without exposing it to high temperatures of 200°C or higher or strong ultraviolet rays. It is an object of the present invention to provide a resist ashing method that can remove resists efficiently.

[Structure of the Invention] (Means for Solving the Problems) The resist ashing method of the present invention is characterized in that a gas containing a fluoride is discharged at atmospheric pressure, and this gas is sprayed onto a resist on a substrate at room temperature or heated. It is something to do.

Examples of the substrate include a glass substrate, a semiconductor substrate, and the like.

As the above-mentioned resist, various resists including a novolak resist can be used.

Examples of the above-mentioned fluoride include CF4, SF6, NF3
, C2F6, etc.

When heating the substrate, a sufficient improvement in the ashing rate can be expected at a temperature of 180° C. or lower, which does not cause thermal damage to the substrate.

Another resist ashing method of the present invention is characterized in that the resist on the substrate is exposed to an atmosphere in which a gas containing fluoride is discharged at atmospheric pressure and added to ozone gas.

As a means of exposing the resist on the substrate to the above atmosphere,
In order to increase the resist ashing speed, a method is adopted in which a gas containing a fluoride is discharged at atmospheric pressure into a container in which the substrate is housed, and ozone gas is supplied through separate gas introduction pipes, and then sprayed onto the resist. is desirable.

It is desirable that the proportion of the atmospheric pressure discharged gas added to the ozone gas is 0.5% by volume or more.

When exposing the resist on the substrate to the above atmosphere, it may be heated at a temperature range (for example, 180° C. or lower) that does not damage elements formed on the substrate, if necessary.

In the resist ashing method according to the present invention, if necessary, ultraviolet rays may be irradiated with an energy intensity that does not damage elements formed on the substrate.

(Function) According to the resist ashing method of the present invention, a gas containing a fluoride is discharged at atmospheric pressure, and this gas is sprayed onto the resist on the substrate at room temperature or heated.
The resist can be ashed more efficiently than the conventional method without causing damage or oxidation to the elements formed on the substrate, which is the case with the conventional method of exposing the resist to an atmosphere or irradiating it with ultraviolet rays in an ozone atmosphere. .

According to another resist ashing method of the present invention, the resist on the substrate is exposed to an atmosphere in which gas containing fluorides is discharged at atmospheric pressure and ozone gas is added, thereby improving the resist ashing efficiency compared to the conventional method. Can ash well. Furthermore, although the ashing rate is slightly lower than the method described above in which a gas containing fluorides is discharged at atmospheric pressure and sprayed onto the resist on the substrate, the risk of contaminating the substrate etc. can be avoided compared to that method. For,
It is extremely useful industrially.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Example 1 FIG. 1 is a partially cutaway schematic diagram showing an ashing device used for resist ashing in this example. The quartz cell 1 is housed in a heater box 2. Inside the quartz cell 1, the substrate holder 3 has a series of transport pipes 5, which will be described later.
It is arranged so as to face the end part (blowout part). A discharge tube 4 for discharging fluoride-containing gas at atmospheric pressure is connected to the quartz cell I via a transport tube 5.

This transport pipe 5 is provided with an on-off valve 6 .

The discharge tube 4 includes a tube body 7 with both ends sealed and the gas transport tube 5 connected to the upper side wall. A glass tube 8 whose upper end is integrated with the earthen wall of the tube body 7 is inserted into the tube body 7 .

A mesh-like electrode 9 is arranged inside the glass tube 8 along the longitudinal direction of the glass tube 8 .

On the outside of the glass tube 8, wire-wound electrodes 1O are wound at predetermined intervals. A power source 11 is connected to the electrodes 9 and 101; The glass tube B includes an introduction tube 1 for supplying gas containing fluoride to the glass tube 8.
2 are connected.

Further, an ozonizer 14 is connected to the quartz cell 1 via a transport pipe 13. This transport pipe 13 is provided with an on-off valve 15 . An 02 gas introduction pipe 1B is connected to the lower side wall of the ozonizer. Note that an exhaust pipe 17 is connected to the quartz cell l.

Next, a resist ashing method will be explained using the above-described ashing apparatus shown in FIG.

First, a novolac resist (product name 0FPR-800 manufactured by Tokyo Ohka Co., Ltd.) is applied onto a silicon substrate on which an element is formed, and dried to cover a resist film with a thickness of 1.5 μm.
A resist pattern is formed by photolithography, and the underlying film is selectively etched and buttered using the resist pattern as a mask. As shown in FIG. It was held in a substrate holder 3.

Next, the on-off valve 1 of the gas transport pipe 13 on the ozonizer 14 side
5 closed. Next, a predetermined amount of CF4 gas is supplied from the gas introduction tube 12 of the discharge tube 4 into the glass tube 8, and a 50Hz Slo
C supplied to the glass tube 8 by applying a high voltage of kV.
F4 gas was excited by discharging at atmospheric pressure.

This excited gas is passed through a transport pipe 5 into a quartz cell l heated to 150°C by a heater box 2 for 204/h.
The resist pattern was ashed by supplying it for 10 minutes under the conditions of r.

Example 2 As in Example 1, the silicon substrate 18 on which the resist pattern remained was held by the substrate holder 3 of the quartz cell 1. Next, 02 gas is introduced from the gas introduction pipe 1B into the ozonizer 14 at a rate of 240II/hr, the ozonizer generates ozone with a concentration of about flog/Nm', and this ozone is passed through the transport pipe 13 and sent to the heater box 2.
CF was supplied into a quartz cell heated to 150°C at a rate of 20ff/hr, and at the same time, as in Example 1, CF was supplied to a discharge tube 4.
24)/hr, 51)/hr, l
It was supplied at og/hr conditions. By supplying these gases for 10 minutes, the resist pattern on the silicon substrate inside the quartz cell I was ashed.

Comparative Example CF Ashing was performed in the same manner as in Example 2, except that the supply of excitation gas to the quartz cell by discharging the gas at atmospheric pressure was reduced to zero.

The decrease in film thickness of the resist pattern after ashing in Example 1.2 and Comparative Example was measured using a Lambda-Ace film thickness meter. The results are shown in Figure 3. Note that the film thickness reduction measurement results were corrected by Talystep.

As is clear from FIG. 3, in the comparative example in which CF 4 gas was discharged at atmospheric pressure and no excitation gas was supplied, the resist ashing rate was approximately 0.12 μm/10 minutes. On the other hand, as in Example 2, the excitation gas was added to 24!
/hr supply (addition ffi to ozone gas; 0.5% by volume), the resist ashing rate is 0.4μ
m/10 minutes, indicating that the supply of excitation gas increases by about 3 to 4 times compared to zero. Further, even if the supply amount of the excitation gas is further increased, the resist ashing rate does not increase sharply, but only increases gradually.

On the other hand, in the method of Example 1 in which only the excited gas obtained by discharging CF4 gas at atmospheric pressure is supplied to the quartz cell, the ashing rate of the resist is 1.4 μm/10 minutes, which shows that the ashing rate is significantly improved.

Example 3 As shown in FIG. 2, similarly to Example 1, a silicon substrate 1B on which a resist pattern remained was held by the substrate holder 3 of the quartz cell 1. Next, as in Example 2, ozone with a concentration of about 110 g/Ns3 is generated using an ozonizer (not shown), and this ozone is passed through a transport pipe 13 into a quartz cell l heated to 150°C by a heater box 2. ! In addition, as in Example 1, an excited gas obtained by discharging CF and gas at atmospheric pressure in a discharge tube (not shown) is supplied to the transport pipe 13 at a rate of 2 g/hr through the transport pipe 5. It was supplied by That is, ozone and excitation gas were not separately supplied into the quartz cell 1, but after these gases were mixed at the front stage of the quartz cell 1, ozone with the excitation gas added was supplied into the quartz cell 1 to perform ashing.

As a result, although an improvement in the ashing rate was observed compared to the method of ashing using only ozone, Example 1.2 could not achieve any high ashing rate. This is because the ozone and excitation gas were mixed before being supplied into the quartz cell, so the active F* and HF in the excitation gas easily lost their activity in the ozone. it is conceivable that.

In addition, in the above example, CF,
It was confirmed that similar effects can be achieved by using an excited gas obtained by discharging another fluoride-containing gas such as SF6 at atmospheric pressure.

In the above example, the substrate was heated to 150° C., but it was confirmed that ashing could be performed efficiently even at room temperature.

[Effects of the Invention] As detailed above, according to the present invention, the resist on the substrate can be quickly decomposed and removed efficiently without exposing the substrate to high temperatures of 200° C. or higher or strong ultraviolet rays that can damage the substrate. A resist ashing method that can be used can be provided.

[Brief explanation of the drawing]

Fig. 1 is a partial cutaway showing one form of the resist ashing device used in Example 1.2 of the present invention. Fig. 3 shows the supply amount of CF4 atmospheric pressure discharge gas (excited gas) and the resist ashing depth (film FIG. 1...Quartz cell, 2...Heater box, 3...
Substrate holder, 4...discharge tube, 5.13...transport tube,
14...Ozonizer, 18...Silicon substrate.

Claims (2)

[Claims] (1) A resist ashing method characterized by discharging a gas containing fluoride at atmospheric pressure and spraying this gas onto a resist on a substrate at room temperature or at a heated temperature. (2) A resist ashing method characterized by exposing a resist on a substrate to an atmosphere in which a gas containing fluoride is discharged at atmospheric pressure and added to ozone gas.