JPH0487319A - Dry-type developing apparatus - Google Patents

Abstract

PURPOSE:To prevent an etching residue from being produced and to enhance the production yield of a semiconductor element by a method wherein the supply amount of a gas containing oxygen for plasma generation use inside a reaction chamber is controlled automatically. CONSTITUTION:While the supply amount of a gas for plasma generation use is controlled automatically, a developing operation is executed fundamentally by the following two processes: a process to remove a silyated layer by transmitted light on the surface; and a process to remove an unexposed resist. While an evacuation speed is being kept definite, the supply amount of the gas containing oxygen is made small in the first process, a pressure inside a chamber 10 is lowered and the surface of the resist is sputter-etched by oxygen ions. Since the surface of the resist is bombarded by the oxygen at high energy during the process, silicon existing on the surface of the resist is sputter-etched without being oxidized and is evacuated. After a prescribed thickness on the surface has been sputter-etched in this manner, the flow rate the gas containing oxygen is increased during the second process, the pressure inside the chamber 10 is increased and a reactive operation is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry developing device that uses reactive ion etching to form a resist pattern in the manufacturing process of semiconductor devices such as ICs and LSIs.

[Prior Art] Conventionally, in the manufacturing process of semiconductor devices such as ICs and LSIs, negative photoresists made of polyisoprene cyclized material mixed with bisazide, or positive photoresists made of novolac resin mixed with quinone diazide compound, were used on the substrate to be processed. Apply type photoresist and apply mercury lamp g through the pattern mask.
A photolithography method is employed in which a resist pattern is formed by exposing the resist to light (wavelength: 436 nm) or i-ray (wavelength: 365 nm) and developing it with a developer.

However, in recent years, semiconductor devices have become even smaller, and the minimum dimension of a resist pattern to be formed on a substrate is 1 μm.
Below, it is entering the region of around 0.5 μm. In such a size range, even if a conventional photolithography method using a developer is used for development, the effects of light reflection during exposure and the exposure system may be affected, especially when a substrate with a step structure is used. Due to problems such as shallow depth of focus,
A problem arises in that sufficient resolution of the resist pattern cannot be obtained.

As a method to solve such problems, JP-A-61-1
In JP 07346, a photoresist containing a photoactive compound and a polymer is exposed through a pattern mask,
A silicon compound is selectively applied to the exposed area to silylate it, and then a resist pattern is formed by etching the unsilylated areas using a reactive ion etching device that generates oxygen plasma. A dry development process has been proposed.

As an example of a reactive ion etching apparatus used in such a dry development process, Japanese Patent Application Laid-Open No. 58-151028
No. 59-140375 discloses means for generating a magnetic field parallel to the surface of the material to be etched at a cathode which is a support for the material to be etched and to which microwave power is applied. A reactive ion etching apparatus is described in which a magnetic field is formed in a direction perpendicular to a cathode which is a support for the material to be etched. is listed.

[Problems to be Solved by the Invention] The dry development process in which the above-mentioned photoresist is silylated and a resist pattern is formed using a reactive ion etching device using oxygen plasma is a method for silylating the photoresist and forming a resist pattern using a reactive ion etching device using oxygen plasma. A resist pattern is formed by etching, taking advantage of the fact that the reactivity of the regions is greatly different. Furthermore, by using the above-mentioned reactive ion etching apparatus, positive ions are accelerated by the plasma sheath formed near the surface of the semiconductor wafer and etch the non-silylated portions of the resist, resulting in large etching anisotropy. Therefore, according to this method, a resist pattern of 0.5 .mu.m or less can be formed with high precision, and high-speed development is possible.

However, when a resist pattern is formed through the process of resist silylation and then reactive ion etching, resist residues may be present on the surface of the silicon wafer where the non-silylated region is etched and exposed.

FIG. 2 is a schematic cross-sectional view showing the state of the residue that exists in the conventional method. Resist 2 on the surface of silicon wafer 1
is applied, and a silylated layer 3 is formed near the surface of the exposed portion of the resist 2 by silylation treatment.

Unexposed portions of the resist, ie, portions without a silylated layer on the surface, are removed by reactive ion etching using oxygen plasma or the like to form a resist pattern. However, residue 4 may be present in the portion where the resist is removed and the surface of the silicon wafer is to be exposed. Such residue becomes a hindrance to subsequent steps for manufacturing semiconductor devices, reducing manufacturing yield.

When the residue 4 is analyzed using an Auger electron spectrometer, it is found to be silicon oxide. This fact suggests that the unexposed resist portion, which should not be silylated, was silylated, and as shown in Figure 3, the resist surface after silylation contains silyls caused by stray light. There is a layer 5 with a thickness of 100~
It was estimated that there were 1,000 students. In other words, it is thought that the silicon in the silylated layer produced by this stray light reacts with oxygen ions during the reactive ion etching process to form silicon oxide, which remains as a residue. It is expected that if the silylated layer can be removed, the generation of residue can be prevented.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dry development method that takes advantage of the advantages of dry development that combines resist silylation and reactive ion etching while preventing the generation of etching residues and thereby improving the manufacturing yield of semiconductor devices. do.

[Means for Solving the Problems] A dry developing device of the present invention etches a resist using plasma of a gas containing oxygen, and includes a reaction chamber in which gas is introduced to generate plasma and etching is performed; means for supplying a gas containing oxygen to the reaction chamber;
The method is characterized by comprising means for generating plasma within the reaction chamber, sample holding means provided within the reaction chamber, and means for automatically controlling the supply amount of the oxygen-containing gas.

The target of dry development, that is, reactive ion etching in the present invention is mainly applied to a semiconductor substrate,
It is a resist that is silylated in a predetermined pattern.

As a preferable silylated resist, for example, a resist made of quinonediazide and an alkali-soluble resin is irradiated with light, heated, and the irradiated areas are selectively silylated with a silane compound such as hexamethyldisilazane or silyl chloride. One example is resist. Here, examples of the alkali-soluble resin include novolac resins having hydroxyl groups, hydroxystyrene resins, and the like.

The present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an example of a continuous dry developing device to which the present invention is applied. This device has process chamber 10
．． A load-lock chamber 20 and a cassette chamber 30 are provided, and a plurality of semiconductor wafers housed in the cassette chamber 30 are sequentially sent one by one through the load-lock chamber 20 to a process chamber IO, and are subjected to dry development processing by etching in the process chamber. The treated wafers sequentially return to the cassette chamber 30 by following the reverse path. In this way, a plurality of wafers can be continuously developed.

Process chamber 1 in which dry development according to the invention is carried out
An electrode 11 is installed inside the 0, and RF power is applied from an RF power source 12 via a matching box 13. It is desirable that the electrode 11 be configured to be capable of applying a magnetic field. The process chamber 10 opens the valve 24 and performs initial evacuation using a rotary pump, and then closes the valve 24 and uses a turbo molecular pump and a rotary pump to perform 2 x 1.0
The pressure is reduced to "' Torr or lower. Also, gas for plasma generation is supplied from the gas cylinder 16 to the process chamber via the mass flow controller 17. The inside of the process chamber 10 is maintained at a predetermined pressure, and then While flowing plasma generation gas at a predetermined flow rate, RF power is applied to the electrode 11 to generate an RF discharge between one electrode and the wall 18 of the process chamber 10 to generate plasma. The ions etch and develop the resist applied to the wafer held on the electrode 11. The progress of the development is monitored by the end point detector 19. The output signal from the detector 19 is input to the control computer 40. The computer 40 operates the mass flow controller 17 according to the signal to automatically control the supply amount of plasma generation gas and also controls the output of the RF power source to the original set value.The load lock chamber 20 and the cassette chamber 30 are 5 x 1O-2T by rotary pump 21
The pressure is reduced to orr or less. Gate valves 22 and 23 are opened during wafer transportation. During a developing operation, valve 24 is closed and valves 25 and 31 are opened. The wafer transport mechanism is not shown.

In the above example, a means is used to automatically control the supply amount of plasma generation gas based on the output signal of the endpoint detector, but the supply amount of plasma generation gas can be controlled in stages using a timer or the like. Means for automatically controlling and simultaneously controlling the output of the RF power source to the original setting value may be used. In addition, the supply amount of plasma generation gas is
It is also possible to control continuously instead of stepwise.

In the present invention, there are basically two steps: a step of removing the silylated layer caused by stray light on the surface by automatically controlling the supply amount of the plasma generation gas, and a step of removing the unexposed resist. Development is performed by That is,
In the first step, the surface layer of the resist is sputter-etched using high-energy plasma particles, and in the second step, the non-silylated portions of the resist to be removed are removed by reactive ion etching under optimal conditions. At this time, the energy of oxygen ions contributing to etching is controlled by controlling the flow rate of the oxygen-containing gas without changing the type of plasma-generating gas in the first and second steps.

That is, it is well known that a plasma sheath is formed near the surface of a sample during etching, and that the potential difference of the plasma sheath is about 50 to 100V. Ions in the plasma bombard the sample surface due to this potential difference, but when the pressure inside the chamber is high, the ions collide with each other and scatter within the sheath, and as a result, the average energy of the oxygen ions reaching the sample surface is will decrease. On the other hand, when the degree of vacuum in the chamber is increased, scattering due to mutual collision of oxygen ions within the sheath is reduced, and the ions reach the sample surface with high energy, resulting in sputter etching of the sample.

In the present invention, while keeping the pumping speed constant, the supply amount of oxygen-containing gas is reduced in the first step (to lower the pressure inside the chamber, and the resist surface is sputter-etched with oxygen ions. This step uses high energy Because the silicon existing on the resist surface is bombarded with oxygen ions, sputter etching is performed without oxidizing the silicon present on the resist surface, and it is exhausted.In this way, after sputter etching a predetermined surface thickness, the As a second step, reactive ion etching is performed by increasing the flow rate of oxygen-containing gas and increasing the pressure inside the chamber.

The determination of the end of the first step, that is, the determination of switching the supply amount of oxygen-containing gas, can be made by determining the amount of silicon in the plasma. That is, a spectrometer is used as the end point detector 19 in the apparatus shown in FIG. 1, the atmosphere inside the chamber 10 is guided, and the emission intensity of Si is measured. When the resist surface of appears, 31
Judgment is made by the decrease in light emission. This time may be set as the end of the first step. It is also possible to use a mass spectrometer as an endpoint detector, and similarly determine the end of the first step at the time when the spectral intensity of Si atoms decreases. Furthermore, the electron temperature in the plasma was measured by the probe method disclosed in Japanese Patent Publication No. 62-23254,
The time of the change can also be set as the end of the first step.

Furthermore, a time-lapse method may be used in which the relationship between the flow rate and the etching rate is determined in advance and the supply amount of the enzyme-containing gas is changed when a predetermined time has elapsed. When using this method, the first step usually takes 8 to 25 minutes of total dry development time.
It is best to set it to about %.

The control computer operates the mass flow controller to control the flow rate based on the output signal when using the endpoint detector, or according to a predetermined program when using the time-lapse method.

The supply amount in the first step is smaller than that in the subsequent steps, but - for boat fishing, it is less than % of the supply amount that maximizes the rate selectivity of reactive ion etching of non-silylated parts to silylated parts. shall be.

Note that the supply amount at which the speed selectivity of this reactive ion etching is maximized varies depending on the equipment used.

The plasma generating gas is not limited to pure oxygen, but also He,
Noble gases such as Ne, Ar, Kr, or Nz.

H,,GO,Co2. A small amount of NH, No, No□, etc. may be supplied together with oxygen.

[Examples] Next, the present invention will be explained using Examples, but the present invention is not limited to these Examples.

Examples 1-4. A quinonediazide-novolac resin resist (trade name: PLASMKASK UCB-JSREL) was used as a comparative example resist.
A resist film having a thickness of 1.5 μm was formed on a silicon wafer using a coater using an ECTRON IC3 (manufactured by Co., Ltd.). Next, using an exposure machine with a numerical aperture of 0.54,
G of mercury lamp through pattern mask! ! (Wavelength 436μ
After irradiating the resist film with 111), a prebaking process was performed at 160°C for 3 minutes, and the g-ray irradiated area was silylated by treatment with hexamethyldisilazane at 60°C for 4 minutes.

A large number of silicon wafers having resist films coated with resist and partially silylated in this manner were prepared, and dry development was performed using the above-mentioned developing device.

Note that the internal volume of the process chamber of the developing device used was 30β, and a magnetron electrode with a diameter of 200 mm was used as the electrode 11. Further, the electrode 11 can be cooled, and the temperature of the silicon wafer held thereon during the development process was 20° C. or lower.

In dry development, after the inside of the process chamber 10 is evacuated to a high vacuum, oxygen gas is introduced into the process chamber as a plasma generation gas, and 13.56M is applied to the electrode 11.
Hz, 1. RF power of ooOW was applied to generate oxygen gas plasma, and the resist was dry-developed using oxygen ions in the plasma.

Table 1 shows the amount of oxygen gas supplied, the pattern width after development, and the presence or absence of residue.

As a result of reactive ion etching of non-silylated parts by varying the amount of oxygen gas supplied, the flow rate at which the etching rate selectivity was maximum was 703 CCM (flow rate converted to standard state (CC/min)). Ta.

Further, the pressure in the process chamber 1O during the development process was 1 to 10 x 1O-3 Torr, and the completion of the first step was determined by a spectrometer.

(Margins below) Table 1 As shown in Table 1, when developing according to the present invention at a low flow rate in the first step and at least twice the flow rate in the second step as the flow rate in the first step, there is no residue at all. I didn't. In addition, the formed resist pattern has approximately a predetermined width (0.5 μm
) It was as expected.

On the other hand, in Comparative Example 1, which is considered to be under optimal conditions for reactive ion etching, the width of the resist pattern was accurate, but a large amount of residue was present.

Note) *: Predetermined pattern width = 0.5 μm [Effects of the Invention] As explained above, according to the present invention, there is no residue after resist development, so the manufacturing yield of semiconductor devices can be improved. Moreover, since the supply amount of the plasma generating gas is changed while the exhaust speed is kept constant, the plasma is not disturbed and development can be carried out stably. Furthermore, since only the flow rate is changed without changing the gas type, high-speed development is possible without reducing throughput.

The present invention can also be applied to a method that does not apply a magnetic field to the cathode,
Furthermore, it can also be applied to various methods using microwave plasma.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the configuration of an embodiment of the dry developing device of the present invention, Fig. 2 is a schematic sectional view showing the state of the residue after dry development, and Fig. 3 is a diagram showing the state of the residue after dry development. FIG. 3 is a schematic cross-sectional view showing the state of a resist. DESCRIPTION OF SYMBOLS 1...Silicon wafer, 2...Photoresist, 3...Silylated layer, 4...Residue, 5...Silylated layer caused by stray light, 1O...Process chamber II... Electrode, 17... Mass flow controller, 19... End point detector. 4, 8, 5 light transmission - T main meaningless layer

Claims (1)

[Scope of Claims] 1) A dry developing device that etches a resist using plasma of a gas containing oxygen, comprising: a reaction chamber in which gas is introduced to generate plasma and etching is performed; a gas containing oxygen is supplied to the reaction chamber; a means for generating plasma in the reaction chamber; a sample holding means provided in the reaction chamber; and a means for automatically controlling the supply amount of the oxygen-containing gas. Device.