JP2003007693A - Optical processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a uniform thickness of an insulating thin film over the whole surface of a semiconductor substrate, by having the surface of the semiconductor substrate irradiated with vacuum ultraviolet rays simultaneously as with thermally oxidized film formation, where the uniformity of the thickness of the insulating thin film higher than 10 nm could not be achieved through only the thermally oxidized film formation. SOLUTION: A processing chamber for forming a process gas atmosphere and a lamp house for receiving a lamp which irradiates vacuum ultraviolet rays and forming a specific atmosphere are separated by a light-transmitting window. A stage for supporting a subject to be processed and a movable light-shielding mask having a slit formed therein disposed near the subject to be processed are provided in the processing chamber. The stage is equipped with a heating mechanism. In the lamp house, a window for transmitting vacuum ultraviolet rays whose wavelengths are not larger than 200 nm is provided at the end of a nearly cylindrical discharge container. A single or a plurality of excimer-generating gases are filled in the discharge container. The optical processing apparatus is characterized by comprising the lamp for radiating the excimer light through the vacuum ultraviolet ray transmitting window by discharging the excimer-generating gas via a dielectric constituting the discharge container and a mechanism for moving the lamp nearly, in parallel to the surface of the subject to be processed with variable speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical processing apparatus used for forming an oxide insulating film on a silicon semiconductor substrate in a semiconductor manufacturing process.

[0002]

_2. Description of the Related Art Silicon dioxide (SiO ₂ ) has a wide forbidden band width of about 9 eV, cannot easily excite electrons in the valence band into the conduction band, and has a high energy barrier height at the interface with Si. Is about 3.1 eV and 3.8 eV for holes.
Therefore, the charge from the Si substrate cannot be easily injected. Therefore, the Si formed on the Si semiconductor substrate
The O ₂ insulating film exhibits excellent insulating properties. In a semiconductor process, as a method of forming an oxide insulating thin film on a silicon semiconductor substrate, a thermal oxide film forming method, a CVD method, PVD
(Sputtering) method.

In particular, the thermal oxide film forming method is currently most widely used in the semiconductor manufacturing process. Here, the thermal oxide film is generally formed by setting a semiconductor substrate in a quartz glass furnace core tube heated by a heater, and then (1) treating a predetermined concentration of oxygen gas with nitrogen gas as a carrier gas. Dry oxygen oxidation, which is carried out by oxidizing it indoors (2)
Wet oxygen oxidation in which nitrogen gas is used as carrier gas to supply oxygen gas through heated water, (3) 100% steam oxidation by heated steam (steam), (4) steam oxidation in which nitrogen gas flows together with steam, (5) hydrogen gas Pyrogenic oxidation that burns oxygen gas with oxygen and supplies the generated high-purity steam, (6) Oxygen partial pressure oxidation in which oxygen gas is passed through liquid oxygen with nitrogen gas as carrier gas, (7) Nitrogen gas and oxygen gas For example, there is hydrochloric acid oxidation in which chlorine gas is added and flowed together.

It is known that the thermal oxide film forming method can obtain a particularly good quality SiO ₂ insulating film. For the gate insulating film and the capacitor insulating film of a MOS transistor, the SiO ₂ insulating film formed by the thermal oxide film forming method is used. An insulating film is used. With the recent miniaturization, high density, and high speed of MOS transistors or capacitors, the thickness of the gate insulating film tends to be thin and highly reliable.

As the performance required for the gate insulating film or the capacitor insulating film, there are no defects such as pinholes,
It can be mentioned that the insulating film has high integrity. More specifically, it has good electrical characteristics such as high withstand voltage and few fixed charges and traps at the interface between the formed SiO ₂ film and silicon, leading to dielectric breakdown when a constant voltage is applied. It takes a long time to reach the point where the total amount of electric charge until dielectric breakdown is large when a constant current continues to flow through the formed SiO ₂ film.

[0006]

With the above-mentioned tendency of thinning the insulating film, it is indispensable to form a uniform film thickness on the entire surface of the Si semiconductor substrate as a requirement other than the above. The thickness of the gate insulating film or the capacitor insulating film is less than 10 nm. Here, when observed at the atomic level, for example, (10
The atomic step on the (0) plane is about 0.18 nm, which is 10 nm.
The thickness of the insulating film is about 2%, and that of 5 nm is about 4%. It is technically very difficult to completely eliminate atomic steps over the entire surface of a semiconductor substrate having a diameter of 8 to 12 inches these days.

[0007] For example, as described in the literature (Semiconductor Process Technology, Hiroyuki Tango, P140-143), the thermal oxide film formation yields a good quality SiO ₂ film, but on the other hand, the thin film formation rate is fast, for example, a thickness of about 10 nm. The SiO2 film of is 9
Approximately 10 minutes in dry oxygen at 00 ° C, 1 in steam at the same temperature
Get in minutes. However, at a low temperature of 900 ° C,
It is known that the stress generated by oxidation does not release stress and the oxidation is slowed in the silicon trench.
Further, it is difficult to control the thickness in 1 minute. Therefore,
With the miniaturization in the future, it has been difficult to obtain a uniform thin film of sub-nanometer to several nanometers on the entire semiconductor substrate by the conventional thermal oxide film formation.

There are various possible reasons for this,
Because it is a thin film, the temperature of the semiconductor substrate must be raised in a short time to maintain a uniform temperature throughout the semiconductor substrate, and the concentration of oxidants such as oxygen molecules and water molecules near the surface of the semiconductor substrate must be uniform. The temperature may be maintained for a short time in order to surely stop the oxidation process at a desired thickness, and the stress caused by the above-described volume expansion due to the oxidation of silicon may be considered.

The present invention has been made in view of the above problems, and an object thereof is 10n over the entire surface of a semiconductor substrate which cannot be achieved only by forming a thermal oxide film.
Uniformity and homogeneity of the thickness of the insulating thin film of m or less are achieved by irradiating the surface of the semiconductor substrate with vacuum ultraviolet light at the same time as heating the object to be irradiated.

[0010]

In order to solve these problems, in the invention of claim 1, a processing chamber for forming a process gas atmosphere and a lamp for emitting vacuum ultraviolet light are housed to form a unique atmosphere. The lamp house is separated by a light transmitting window, a stage on which the object to be processed is placed in the processing chamber, and a light-shielding mask having a slit movable near the processing chamber is disposed. The stage is provided with a heating mechanism, the lamp house is provided with a vacuum ultraviolet light transmission window of 200 nm or less at the end of a substantially cylindrical discharge vessel, and a single or plural excimer is provided inside the discharge vessel. A lamp that encloses the generated gas, discharges the excimer generated gas through a dielectric that constitutes the discharge container, and emits excimer light from a window portion that transmits the vacuum ultraviolet light; and the lamp, It is an optical processing device according to claim in which the mechanism for moving the surface substantially parallel and variable speed of the workpiece is disposed.

According to a second aspect of the present invention, there is provided the optical processing device according to the first aspect, wherein the stage includes a rotating mechanism.

According to a third aspect of the present invention, there is provided the optical processing apparatus according to the first or second aspect, wherein the unique atmosphere is nitrogen or argon.

[0013]

Next, the operation of the present invention will be described. According to the present invention of claim 1, the object to be processed is heated by the heating mechanism (heater) installed on the stage on which the object to be processed is placed, and at the same time, by vacuum ultraviolet light emitted from the lamp, Since the process gas atmosphere near the surface of the object to be processed is activated and the object to be processed is maintained at an appropriate temperature, the processing of the activated process gas is precisely and uniformly controlled.

The degree of treatment of the object to be treated (for example, the thickness of the insulating thin film to be formed) depends on the temperature of the object to be treated, the partial pressure of the process gas, the radiation intensity of the irradiated light, and the like. Further, by moving the lamp substantially parallel to the surface of the object to be processed and at a variable speed, the irradiation amount of light at a specific portion of the object to be processed can be changed. Therefore, the lamp is moved at a constant speed in advance, the degree of processing of the object to be processed is measured, and the irradiation amount distribution of the object to be processed required from the degree of processing and the illuminance amount of light is known, and this is realized. The desired processing can be performed.

A lamp is provided at the end of a substantially cylindrical discharge vessel.
A window portion that transmits vacuum ultraviolet light of 00 nm or less is provided, and excimer light having an emission wavelength of 200 nm or less generated inside the discharge container is directed from the window surface toward an object to be processed, with the longitudinal axis of the discharge container as a center. Concentric irradiance distribution, for example,
A Gaussian distribution in which the irradiance is highest at the center and the illuminance decreases as the distance from the center increases can be obtained.

According to the invention as set forth in claim 2, the mechanism for moving the lamp substantially parallel to the surface of the object to be processed and variably changing the speed is such that the peripheral end of the object to be processed is rotated from the rotation center of the object to be processed. It is possible to simplify only the straight line connecting the portions, and further, the processing amount of a specific portion of the processing object can be varied in the radial direction of the rotation center, or the processing amount of the entire surface of the processing object can be made uniform.

According to the third aspect of the present invention, the vacuum ultraviolet light emitted from the window portion of the lamp in the lamp house is suppressed from being absorbed by the atmosphere as much as possible, and the process gas atmosphere and the object to be processed are reduced. The surface will be efficiently absorbed and irradiated.

When irradiating with vacuum ultraviolet light, it is possible to use a rod-shaped ultraviolet lamp by arranging it in parallel with the object to be treated, but when the rod-shaped ultraviolet lamp is used, the utilization efficiency of the generated light is extremely poor. There is a problem that becomes.

Therefore, as an ultraviolet lamp having a strong central illuminance, a "window portion for transmitting vacuum ultraviolet light of 200 nm or less is provided at an end portion of a substantially cylindrical discharge vessel according to claim 1.
A lamp that encloses a single or a plurality of excimer-producing gases inside the discharge vessel, discharges the excimer-producing gas through a dielectric material forming the discharge vessel, and emits excimer light from the vacuum ultraviolet light transmitting window. " (Hereinafter referred to as a head-on type barrier lamp) will be used. When using a head-on type barrier lamp, the strength of the central part is strong,
This is because the utilization efficiency of the generated light becomes high.

However, in the case of a head-on type barrier lamp, the illuminance distribution is approximately concentric and Gaussian, and exposure using a light-shielding mask is necessary to easily calculate the integrated light amount profile. . In the actual film formation, the uniform film formation is not possible due to the existence of the gas concentration and the substrate temperature distribution in the vicinity of the substrate when the irradiation is performed at a constant speed, and a predetermined integrated light amount (irradiation amount) distribution is required on the semiconductor substrate. Is. When a combination of a light-shielding mask and a head-on type barrier lamp is used for irradiation, it is possible to achieve a desired irradiation amount distribution on the semiconductor substrate because the desired integrated light amount profile can be obtained without error by changing the irradiation speed. Became.

Now, the head-on type barrier lamp will be described. FIG. 8 shows a head-on type barrier lamp 100.
It is sectional drawing (equivalent to the barrier lamp 5 of FIG. 1). The discharge vessel is composed of an outer tube 102 made of quartz glass and an inner tube 101 made of quartz glass, and a window portion 103 made of synthetic quartz glass is provided at one end of the outer tube 102. Xenon or the like is enclosed in the discharge space 114, and vacuum ultraviolet light is emitted from the window 103.

The inner tube 101 has a hermetically sealed structure at the ends 104 and 105. The outer electrode 112 is a circular tubular electrode that also functions as a light reflecting plate made of two electrode members obtained by bending an aluminum plate into a semicircular plate shape. Like the outer electrode, the inner electrode 113 is composed of two electrode members formed by bending an aluminum plate into a semicircular plate shape, and the electric input to the inner electrode 113 is connected to the spiral spring 106 provided at one end of the inner electrode. This is done by connecting to the power supply 111 through the high voltage lead 109.

FIG. 9 is a cross-sectional view of another type of head-on type barrier lamp. Inner electrode 113, Mo wire 107, Mo wound around several columns in a coil shape without using an inner tube
It has a foil 108. The outer electrode 112 has the same structure as that shown in FIG. It is an electrode. Other than this, for example, the lamps disclosed in JP-A-7-226190 and JP-A-8-236084 can be applied.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention. The lamp house 1 provided with a drive table 4 whose speed can be varied on the XY-2 axis plane is kept in an inert atmosphere of nitrogen or argon, and the barrier lamp 5 is fixed to the drive table 4. The barrier lamp 5 has a cylindrical shape and can emit excimer light having the illuminance distribution of Gaussian distribution shown in FIG. 3 from the end of the discharge vessel.

Further, the processing chamber 2 adjacent to the lamp house 1 in which the object to be processed is arranged has a structure in which a processing gas for maintaining a partial oxygen partial pressure of a predetermined concentration can be flowed and exhausted to a reduced pressure. ing. The semiconductor substrate, which is the object to be processed, is placed on the stage 8 having the heater 81 built therein and heated to about 450 ° C., and excimer light can be emitted from the barrier lamp 5 at a distance of about 120 mm through the transmission window 3. A light-shielding mask 6 having a width of 30 mm is arranged at a distance of several mm from the semiconductor substrate 7 and is moved in accordance with the movement of the lamp 5 in the X direction, which is for partially irradiating the excimer light.

FIG. 2 shows the semiconductor substrate 7 in the gap between the light-shielding masks 6.
It is shown that the portion B is positioned, the center of the barrier lamp 5 is positioned in the gap of the light shielding mask 6, and the barrier lamp 5 is moved while changing the speed. Part A is semiconductor substrate 7
A region passing through the center of B, and a portion B is a region passing through the edge of the semiconductor substrate 7. In the figure, the semiconductor substrate and the stage are shown by solid lines for convenience.

In the processing chamber, an oxidant is used as a process gas for forming an oxide film on a silicon semiconductor substrate. Specifically, nitrogen is used as a buffer gas, dry oxygen and water vapor as the oxidant, and Atmospheric gas to which chlorine gas is further added is introduced from the processing gas supply port 21 and exhausted from the processing gas exhaust port 22 to form an oxygen partial pressure atmosphere of a predetermined concentration (for example, 5 to 30%).

FIGS. 4 (a) and 4 (b) are the dose distributions of the portions A and B on the substrate necessary for forming a uniform oxide insulating film, and FIGS. 5 (a) and 5 (b) are The irradiation time (1 / moving speed of the lamp) at each position of the lamp for realizing the required irradiation amount distribution is shown in FIGS. 6 (a) and 6 (b).
It shows the irradiation amount distribution obtained by actually irradiating with the irradiation time of (a) and (b). The moving speed of the lamp is changed by associating the temperature of the substrate with the process gas atmosphere near the surface of the substrate.

FIG. 7 shows a second embodiment of the present invention. The drive table 4 in the lamp house 1 has one axis, and the stage 8 in the processing chamber 2 can be rotated at a constant speed. Reference numeral 82 is a turntable. The required dose distribution is a distribution symmetrical with respect to the center of the substrate in the radial direction, and is the same as in FIG. In this case, assuming that the irradiation time at each position in the X direction of the lamp is the time obtained by multiplying the value shown in FIG. 5 (a) by the square of the diameter distance, the actually obtained irradiation dose distribution is as shown in FIG. (A)
Became the same.

As a concrete result, in Example 1, there is no defect such as a pinhole, and an insulating thin film of 10 nm or less on a silicon semiconductor substrate has a thickness variation of ± 7%.
The uniform film (oxide film) can be realized, and in Example 2, the uniform film (oxide film) with the variation in thickness being within ± 5% can be realized.

[0031]

According to the present invention, the uniformity and homogeneity of the thickness of the insulating thin film of 10 nm or less, which cannot be achieved only by forming the thermal oxide film, simultaneously heats the silicon semiconductor substrate, and at the same time, vacuum ultraviolet rays are applied to the surface of the semiconductor substrate. By irradiating with light, the thickness of the insulating thin film can be made uniform over the entire surface of the semiconductor substrate.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a first embodiment of an optical processing device of the present invention.

FIG. 2 is a diagram for explaining movement of a silicon semiconductor substrate and a light shielding mask in the first embodiment.

FIG. 3 is a diagram showing an irradiance distribution of a barrier lamp.

FIG. 4 is a dose distribution diagram for forming a uniform oxide insulating film.

FIG. 5 is a diagram showing irradiation time (1 / moving speed) at each position of the lamp for realizing a required irradiation amount distribution.

FIG. 6 is a diagram showing an irradiation amount distribution actually obtained with the irradiation time of FIG.

FIG. 7 is a schematic diagram showing the configuration of a second embodiment of the optical processing device of the present invention.

FIG. 8 is a cross-sectional view of a head-on type barrier lamp.

FIG. 9 is a cross-sectional view of another type of head-on type barrier lamp.

[Explanation of symbols]

1 lamp house 2 processing room 21 Processing gas supply port 22 Process gas exhaust port 3 transparent window 4 drive stand 5 barrier lamps 6 Shading mask 7 Semiconductor substrate 8 stages 81 heater 82 turntable 100 head-on type barrier lamp 101 inner tube 102 outer tube 103 window 104 edge 105 end 106 spring 107 Mo line 108 Mo foil 109 high voltage lead 110 high voltage lead 111 power supply 112 outer electrode 113 inner electrode 114 discharge space

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenichi Hirose             1194 Sado, Bessho Town, Himeji City, Hyogo Prefecture Usio             Electric Co., Ltd. F-term (reference) 5F045 AA20 AB32 AC11 AC15 AD08                       BB02 EB02 EC03 EK12 EK19                       EK23

Claims (3)

[Claims] 1. A processing chamber for forming a process gas atmosphere and a lamp house for accommodating a lamp that emits vacuum ultraviolet light to form a unique atmosphere are separated by a light transmission window, and the inside of the processing chamber is covered. A stage on which the object to be treated is placed and a light-shielding mask having a slit that can be moved close to the chamber to be treated are arranged, the stage is equipped with a heating mechanism, and the lamp house has a substantially cylindrical shape. 2 at the end of the discharge vessel
The discharge vessel is provided with a window portion that transmits vacuum ultraviolet light of 00 nm or less, and a single or a plurality of excimer-producing gas is enclosed inside the discharge vessel to discharge the excimer-producing gas through the dielectric material forming the discharge vessel. A light processing apparatus comprising: a lamp that emits excimer light from the window portion; and a mechanism that moves the lamp substantially parallel to the surface of the object to be processed and at a variable speed. 2. The optical processing device according to claim 1, wherein the stage includes a rotation mechanism. 3. The optical processing apparatus according to claim 1, wherein the specific atmosphere is nitrogen or argon.