JP3716762B2 - Light processing equipment - Google Patents

Description

[0001]
BACKGROUND 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]
[Prior art]
Silicon dioxide (SiO ₂ ) has a wide band gap of about 9 eV, and cannot easily excite electrons in the valence band to the conduction band, and the energy barrier height at the interface with Si is about 3. The charge is as high as 1 eV and 3.8 eV with respect to holes, so that charges from the Si substrate cannot be easily injected. For this reason, the SiO ₂ insulating film formed on the Si semiconductor substrate exhibits excellent insulating properties. In a semiconductor process, a method for forming an oxide insulating thin film on a silicon semiconductor substrate includes a thermal oxide film forming method, a CVD method, a PVD (sputtering) method, and the like.
[0003]
In particular, the thermal oxide film forming method is currently most widely used in semiconductor manufacturing processes. Here, the thermal oxide film formation is generally performed by setting a semiconductor substrate in a quartz glass furnace core tube heated by a heater, and then (1) treating oxygen gas of a predetermined concentration using nitrogen gas as a carrier gas. (2) wet oxygen oxidation in which oxygen gas is supplied through heated water using nitrogen gas as a carrier gas, (3) 100% steam oxidation with heated steam (steam), (4) ) Steam oxidation in which nitrogen gas is flowed with steam, (5) Pyrogenic oxidation in which hydrogen gas and oxygen gas are burned and high purity water vapor is generated, (6) Nitrogen gas is used as carrier gas and oxygen gas is passed through liquid oxygen There are oxygen partial pressure oxidation to flow, (7) hydrochloric acid oxidation to flow by adding chlorine gas together with nitrogen gas and oxygen gas.
[0004]
The thermal oxide film forming method is known to obtain a particularly good SiO ₂ insulating film, and the insulating film of SiO ₂ formed by the thermal oxide film forming method is used for the gate insulating film and capacitor insulating film of the MOS transistor. It 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.
[0005]
As the performance required for the gate insulating film or the capacitor insulating film, there is no defect such as pinholes and the integrity as an insulating film is high. More specifically, the dielectric breakdown is high when a constant voltage is applied because the dielectric strength is high and the electric characteristics such as fixed charges and traps are small at the interface between the formed SiO ₂ film and silicon. For example, the amount of charge until the dielectric breakdown is increased when a constant current continues to flow through the formed SiO ₂ film.
[0006]
[Problems to be solved by the invention]
Along with the above-mentioned trend 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 request other than the above, but the thickness of the current gate insulating film or capacitor insulating film Has reached 10 nm. Here, when observed at the atomic level, for example, the atomic step on the (100) plane of single crystal Si is about 0.18 nm, about 2% with respect to the thickness of the insulating film of 10 nm, and about 5 nm with respect to that of 5 nm. 4%. It is technically very difficult to completely eliminate atomic steps on the entire surface where the diameter of a semiconductor substrate of recent times reaches 8 to 12 inches.
[0007]
For example, as described in the literature (Semiconductor Process Technology edited by Hiroshi Tangu, P140-143), the formation of a thermal oxide film can provide a high-quality SiO ₂ film, but has a high thin film formation speed, for example, a SiO ₂ film having a thickness of about 10 nm. Can be obtained in about 10 minutes in dry oxygen at 900 ° C. and in about 1 minute in water vapor at the same temperature. However, it is known that at a low temperature of 900 ° C., release of stress generated by oxidation does not proceed, and oxidation is slowed down in a silicon trench (trench), and it is difficult to control the thickness in one minute. Therefore, with the miniaturization in the future, it has been difficult to obtain a uniform thin film of about sub-nanometers to several nanometers over the entire semiconductor substrate by conventional thermal oxide film formation.
[0008]
There are various reasons for this, but because it is a thin film, the temperature of the semiconductor substrate must be raised in a short time to maintain the entire semiconductor substrate at a uniform temperature. To maintain a uniform concentration of oxidizers such as oxygen and water molecules, to ensure that the oxidation process stops at the desired thickness, the temperature must be lowered in a short time, and the volume expansion due to the oxidation of silicon described above It is possible to generate stress due to this.
[0009]
The present invention has been made in view of the above problems, and the object of the present invention is to provide a uniform and uniform thickness of an insulating thin film of 10 nm or less over the entire surface of a semiconductor substrate that cannot be achieved only by forming a thermal oxide film. This is achieved by irradiating the surface of the semiconductor substrate with vacuum ultraviolet light simultaneously with heating of the irradiated object.
[0010]
[Means for Solving the Problems]
In order to solve these problems, in the invention of claim 1, the processing chamber for forming the process gas atmosphere and the lamp house for accommodating the lamp for emitting vacuum ultraviolet light and forming the nitrogen gas or argon gas atmosphere are light A stage that is separated by a transmission window and in which the object to be processed is placed in the processing chamber, and a slit that is movable in the X direction on the XY-2 axis plane that is close to the object to be processed and parallel to the object to be processed The stage is equipped with a heating mechanism, and the lamp house has a window portion that transmits vacuum ultraviolet light of 200 nm or less at the end of a cylindrical discharge vessel. A single or plural excimer generating gas is sealed inside the discharge vessel, the excimer generating gas is discharged through a dielectric constituting the discharge vessel, and excimer light is emitted from the window. And a mechanism for moving the lamp parallel to the surface of the object to be processed and at a variable speed so that the center of the lamp is located in the gap of the light shielding mask. In order to irradiate the light, the shading mask is positioned when the center of the lamp is positioned in the gap of the shading mask and the lamp is moved in parallel with the surface of the workpiece and moved in the X direction. An optical processing apparatus for forming an oxide film on a silicon semiconductor substrate, characterized by being moved in accordance with the movement of the direction.
[0011]
The invention according to claim 2 is the optical processing apparatus according to claim 1, wherein the stage includes a rotation mechanism.
[0013]
[Action]
Next, the operation of the present invention will be described. According to the first aspect of the present invention, the object to be processed is heated by a heating mechanism (heater) installed on a 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 in the vicinity of the surface of the workpiece is activated and the workpiece is maintained at an appropriate temperature, the treatment of the activated process gas is controlled precisely and uniformly.
[0014]
The degree of processing of the object to be processed (for example, the thickness of the insulating thin film to be formed) depends on the temperature of the object to be processed, the partial pressure of the process gas, the radiation intensity of the irradiated light, and the like. Further, by moving the lamp parallel to the surface of the object to be processed and at a variable speed, it is possible to vary the amount of light irradiation at a specific portion of the object to be processed. Therefore, by moving the lamp at a constant speed in advance, measuring the degree of processing of the object to be processed, and making the required irradiation amount distribution of the object to be processed known from this degree of processing and the amount of illuminance of light, this is realized. Desired processing can be performed.
[0015]
The lamp has a window portion that transmits vacuum ultraviolet light of 200 nm or less at the end of a cylindrical discharge vessel, and excimer light having an emission wavelength of 200 nm or less generated inside the discharge vessel is processed from the window surface. A concentric irradiance distribution centering on the longitudinal axis of the discharge vessel toward the object, for example, a Gaussian distribution in which the irradiance is highest at the center and decreases as it moves away from the center. In addition, by making the inside of the lamp house an inert atmosphere, the vacuum ultraviolet light emitted from the lamp window in the lamp house is suppressed from being absorbed by the atmosphere as much as possible, and the process gas atmosphere and the surface of the object to be processed Will be absorbed and irradiated efficiently.
[0016]
According to the second aspect of the present invention, the mechanism for moving the lamp parallel to the surface of the object to be processed and at a variable speed is a straight line connecting the rotation center of the object to be processed and the circumferential end of the object to be processed. In addition, the processing amount at a specific portion of the object to be processed can be varied or the processing amount of the entire surface of the object to be processed can be made uniform with respect to the radial direction of the center of rotation.
[0018]
In addition, it is conceivable to use a rod-shaped ultraviolet lamp in parallel with the object to be processed when irradiating with vacuum ultraviolet light. However, when a rod-shaped ultraviolet lamp is used, the efficiency of using the generated light becomes extremely poor. is there.
[0019]
Therefore, as an ultraviolet lamp having a strong central illuminance, “a window portion that transmits vacuum ultraviolet light of 200 nm or less is provided at the end of the cylindrical discharge vessel according to claim 1, and the discharge vessel has a single or A lamp that encloses a plurality of excimer generation gases, discharges the excimer generation gas through a dielectric that constitutes the discharge vessel, and emits excimer light from the vacuum ultraviolet light transmission window ”(hereinafter referred to as a head-on type barrier lamp) Will be used. This is because when the head-on type barrier lamp is used, the strength of the central portion is strong and the utilization efficiency of the generated light is increased.
[0020]
However, in the case of a head-on type barrier lamp, it has an illuminance distribution having a substantially Gaussian distribution concentrically, and exposure using a light-shielding mask is necessary to easily calculate the integrated light amount profile. In actual film formation, uniform film formation cannot be achieved with the gas concentration and substrate temperature distribution in the vicinity of the substrate when irradiation is performed at a constant speed, and a predetermined integrated light intensity (irradiation amount) distribution is required on the semiconductor substrate. It is. When irradiating with a combination of a light-shielding mask and a head-on type barrier lamp, the desired dose distribution can be achieved on the semiconductor substrate because the desired integrated light intensity profile can be obtained without error by irradiating at a variable speed. It became.
[0021]
Here, the head-on type barrier lamp will be described.
FIG. 8 is a cross-sectional view of the head-on type barrier lamp 100 (corresponding to the barrier lamp 5 in 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 synthetic quartz glass window 103 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 portion 103.
[0022]
The inner tube 101 has a sealed structure at the end portions 104 and 105. The outer electrode 112 is a tubular electrode that also serves as a light reflecting plate composed of two electrode members obtained by bending an aluminum plate into a semicircular shape. Like the outer electrode, the inner electrode 113 is composed of two electrode members obtained by bending an aluminum plate into a semicircular shape, and an electric input to the inner electrode 113 is connected to a 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.
[0023]
FIG. 9 is a cross-sectional view of another type of head-on type barrier lamp. It has an internal electrode 113, a Mo wire 107, and a Mo foil 108 that are wound around several columns without using an inner tube. The outer electrode 112 has the same structure as that shown in FIG.
Electrode. Other than this, it is possible to apply a lamp as disclosed in, for example, Japanese Patent Laid-Open Nos. 7-226190 and 8-236084.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a first embodiment of the present invention. The lamp house 1 in which the drive base 4 capable of varying the speed on the XY-2 axis plane is maintained in an inert atmosphere of nitrogen or argon, and the barrier lamp 5 is fixed to the drive base 4. The barrier lamp 5 has a cylindrical shape and can irradiate excimer light having an illuminance distribution of Gaussian distribution shown in FIG. 3 from the end of the discharge vessel.
[0025]
A processing chamber 2 adjacent to the lamp house 1 in which an object to be processed is arranged has a structure in which a processing gas for maintaining an oxygen partial pressure of a predetermined concentration can be flowed and exhausted to a reduced pressure. A semiconductor substrate, which is an object to be processed, is placed on a stage 8 including a heater 81 and heated to about 450 ° C., and excimer light can be irradiated from the barrier lamp 5 about 120 mm away through the transmission window 3. A light-shielding mask 6 having a width of 30 mm is arranged several mm away from the semiconductor substrate 7 and is moved in accordance with the movement of the lamp 5 in the X direction. This is for partial irradiation with excimer light.
[0026]
FIG. 2 shows that the portion B of the semiconductor substrate 7 is positioned in the gap of the light shielding mask 6, 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 a region passing through the center of the semiconductor substrate 7, and part B is a region passing through the end of the semiconductor substrate 7. In the figure, the semiconductor substrate and the stage are indicated by solid lines for convenience.
[0027]
In the processing chamber, an oxidant is used as a process gas for forming an oxide film on the silicon semiconductor substrate. Specifically, nitrogen is used as a buffer gas, and dry oxygen, water vapor, and these are further used as an oxidant. An atmosphere gas added with chlorine gas is introduced from the processing gas supply port 21 and discharged from the processing gas exhaust port 22 to form an oxygen partial pressure atmosphere (for example, 5 to 30%) having a predetermined concentration.
[0028]
4 (a) and 4 (b) show the dose distribution of the A part and the B part on the substrate necessary for forming a uniform oxide insulating film, and FIGS. 5 (a) and 5 (b) are required. 6 (a) and 6 (b) show the irradiation time (1 / lamp moving speed) at each position of the lamp for realizing the irradiation amount distribution shown in FIGS. 6 (a) and 6 (b). The irradiation dose distribution obtained by actually irradiating with is shown. The lamp moving speed is varied in association with the process gas atmosphere in the vicinity of the substrate surface and the substrate temperature.
[0029]
FIG. 7 shows a second embodiment of the present invention. The driving 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 denotes a turntable. The required dose distribution is a distribution symmetrical in the radial direction about the center of the substrate, and is the same as FIG. In this case, assuming that the irradiation time at each position in the X direction of the lamp is a value obtained by multiplying the value shown in FIG. 5 (a) by the square of the distance of the diameter, the actually obtained irradiation dose distribution is as shown in FIG. It became the same as (a).
[0030]
As a concrete result, in Example 1, a uniform film (oxide film) having no defects such as pinholes and having an insulating thin film of 10 nm or less on a silicon semiconductor substrate with a thickness variation within ± 7% is obtained. In Example 2, a uniform film (oxide film) having a thickness variation of within ± 5% could be realized.
[0031]
【The invention's effect】
According to the present invention, the surface of the semiconductor substrate is irradiated with vacuum ultraviolet light at the same time as heating the silicon semiconductor substrate to achieve uniformity and homogeneity of the thickness of the insulating thin film of 10 nm or less, which could not be achieved only by forming the thermal oxide film. Thus, the thickness of the insulating thin film can be made uniform over the entire surface of the semiconductor substrate.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a configuration of a first embodiment of an optical processing apparatus of the present invention.
FIG. 2 is a diagram for explaining the 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 / movement speed) at each position of a lamp for realizing a required irradiation amount distribution;
6 is a diagram showing a dose distribution actually obtained with the irradiation time of FIG. 5. FIG.
FIG. 7 is a schematic view showing a configuration of a second embodiment of the light processing apparatus 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 embodiment of a head-on type barrier lamp.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lamphouse 2 Processing chamber 21 Processing gas supply port 22 Processing gas exhaust port 3 Transmission window 4 Drive stand 5 Barrier lamp 6 Shading mask 7 Semiconductor substrate 8 Stage 81 Heater 82 Turntable 100 Head-on type barrier lamp 101 inner tube 102 outer tube 103 window portion 104 end portion 105 end portion 106 spring 107 Mo wire 108 Mo foil 109 high voltage lead 110 high voltage lead 111 power source 112 outer electrode 113 inner electrode 114 discharge space

Claims (2)

A processing chamber that forms a process gas atmosphere and a lamp house that contains a lamp that radiates vacuum ultraviolet light and that forms an atmosphere of nitrogen gas or argon gas are separated by a light transmission window. And a light-shielding mask having slits that are movable in the X direction on the XY-2 axial plane parallel to the object to be processed and disposed near the object to be processed. In the lamp house, the end of the cylindrical discharge vessel is provided with a window that transmits vacuum ultraviolet light of 200 nm or less, and an excimer-generating gas composed of a single or a plurality of gases is contained inside the discharge vessel. The excimer-generating gas is discharged through a dielectric that forms the discharge vessel, and the excimer light is emitted from the window, and the center of the lamp is positioned in the gap of the light-shielding mask. And a mechanism for moving the substrate in parallel with the surface of the object to be processed at a variable speed, and for partially irradiating the object to be processed with the excimer light, the light-shielding mask has a center of the lamp. Of the silicon semiconductor substrate, wherein the lamp is moved in parallel with the surface of the object to be processed, and moved in the X direction when the lamp is moved in the X direction. An optical processing apparatus for forming an oxide film. The optical processing apparatus according to claim 1, wherein the stage includes a rotation mechanism.

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