JP3157510B2 - Light excitation treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding photoexcitation processing methods such as photoexcitation CVD, photoexcitation etching, and lithography, of light emitted from a light source, light having a wavelength that damages a substrate is blocked before reaching the substrate. For the purpose, in a light excitation processing method of irradiating a sample on a substrate with light from a light source through a spectral member and performing a predetermined process, the spectral member is made of substantially the same material as that of the substrate or of the substrate. It was configured to be a compound containing a composition element. Further, the angle of the light-splitting member can be adjusted.

[Industrial applications]

The present invention relates to a photoexcitation processing method such as photoexcitation CVD, photoexcitation etching, and lithography.

2. Description of the Related Art In recent years, improvements in lithography technology and CVD methods are expected with the increase in integration and density of semiconductor devices.

Here, for example, in lithography technology, photoexcitation lithography using an exposure medium having a high theoretical resolution is used in response to a demand for miniaturization accompanying high integration of LSI. Also,
In the CVD method, temperature control is performed to control the film quality,
A photo-excited CVD method for, for example, vibrationally exciting material molecules is used.

As described above, in order to enable a high-performance operation of a semiconductor device, a light excitation processing method for performing various processes using high-energy light as a light source is required.

[Conventional technology]

Photoexcitation processing method in semiconductor processing technology (photoexcitation CV
D, photoexcitation etching, photoexcitation lithography, etc.)
The purpose is to improve the light absorption characteristics of the source gas, the use of a high excited state, or the resolution by short-wavelength light.

Hereinafter, among such light excitation processing methods, light excitation CVD and lithography will be described as examples.

Photoexcited CVD is a chemical vapor deposition method using light energy. And the mainstream of today is a method of photodecomposing a material gas by ultraviolet light. This eliminates the need to raise the substrate temperature as in thermal CVD, and enables temperature control for film quality control. A low-pressure mercury lamp or the like can be used as an ultraviolet light source to form a thin film of 1 μm or less.

In lithography, miniaturization of semiconductor devices, especially LSI
With the demand for higher integration, technology development using an exposure medium having a high resolution in principle as a light source has been promoted. Here, lithography using X-ray exposure will be described as an example.

X-ray exposure has less diffraction and interference than light of light exposure, and can perform pattern transfer with high accuracy. In X-ray exposure, synchrotron radiation (hereinafter referred to as SR light) is used rather than an electron beam-excited X-ray source. This is because the electron beam excited X-ray source has a finite size and is a divergent beam, which affects the accuracy of the transfer pattern. SR light is high-intensity light contained in electromagnetic waves emitted by electrons moving at a speed close to high speed in a magnetic field in an electron synchrotron. Light ranges from infrared rays to X-rays, and is remarkably superior to other X-ray sources in parallelism, intensity and brightness. In particular, soft X-rays having a wavelength of 1 to 5 nm have an energy density of 100 mW / cm ² or more on a wafer.

In the conventional light excitation processing method, a sample is irradiated with light from a light source directly or selected through a spectral member such as a diffraction grating, a thin film filter, or a multilayer mirror to irradiate the sample. This is because ultraviolet light and SR light include light unnecessary for photolysis and exposure.

[Problems to be solved by the invention]

When light of a specific wavelength out of the light included in ultraviolet light and SR light is irradiated on a substrate on which a sample is mounted, for example, a semiconductor substrate, it damages the substrate surface and the inside. And
Such damage ultimately results in performance degradation of the semiconductor circuit. Further, in the X-ray region, since the absorption coefficient of the substance is small, the damage penetrates deep into the substrate, and it is difficult to remove the damage even in a subsequent process. For this reason, it is required that light having a wavelength that damages the substrate be blocked by some means before reaching the substrate.

As a method of directly irradiating the sample with the light from the light source and further blocking the light of the unnecessary wavelength, there is a method in which the light source is processed such as an undulator to obtain a desired spectral region width. However, such a method requires a large area CVD.
And the output intensity is not enough to perform etching.

Further, in the method of disposing various light-splitting members between the light source and the sample, for example, the diffraction grating has an excessively large dispersion and weakens the light, and thus is not suitable for CVD or etching of the sample. Further, a thin film filter made of a metal or an insulator is extremely thin (1000 to 2000 mm) and thus is easily broken, and is often broken by radiated light. Furthermore, a multilayer mirror cannot block long wavelength light. (The President stated, "Radiation-excited CVD,
Tsuneo Urisu, Optical Technology Contact Record, Vol. 25, No. 3, 1987 ". As described above, when the sample on the substrate is subjected to the optical excitation processing,
There is a problem that it is difficult to effectively block light having a wavelength that damages the substrate, out of the light emitted from the light source to the sample.

In view of the above problem, the following means are provided for the purpose of blocking light having a wavelength that damages the substrate before reaching the substrate.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention provides a light source 1 from a light source.
Is irradiated on the sample on the substrate 7 through the spectral member 5 to perform a predetermined process.
Is made of substantially the same material as the substrate 7 or a compound containing a composition element of the substrate. Further, the angle of the beam splitting member 5 can be adjusted.

[Action]

When the light-splitting member 5 is made of a compound containing substantially the same material or the same composition as the substrate, light having a wavelength that damages the substrate 7 is absorbed by the light-splitting member 5 before the substrate 7 is irradiated. Then, the sample and the substrate 7 are irradiated in a state where the light having a wavelength that damages the substrate 7 is attenuated.
The damage to the surface and the inside of the is reduced.

The light required for the light excitation processing on the sample is not so much absorbed by the spectral member, and does not significantly affect the processing such as the light excitation CVD and lithography.

Also, the angle of the light separating member 5 is adjusted so that the light 1
Among them, light of any wavelength can be selected. For example, when the light-splitting member 5 is a reflective film in photoexcitation lithography,
By changing the angle of incidence, it becomes possible to select only the light necessary for exposure from the light 1 from the light source.

〔Example〕

FIG. 1 is a sectional view showing a main part of an apparatus for photoexcited growth of silicon by SR light 1 according to an embodiment of the present invention.

The SR light 1 passes through a beam line 2 and a flange 3a and enters a vacuum chamber 4 having a silicon mirror 5 as a spectral member.

Here, the SR light 1 is radiated from an electron storage ring (not shown), and radiated light having a certain wavelength (for example, about 0.5 nm) or less is almost absorbed by a parallel reflection mirror (not shown). The above-described ultraviolet light may be used instead of the SR light.

The beam line 2 refers to a region from such an electron storage ring to a growth chamber where the silicon substrate 7 is located. Then, up to the vacuum chamber 4, at least 10 ^-9
It must be in a high vacuum of about Torr.

The silicon mirror 5, which is a light-splitting member, is provided on the path of the SR light 1 between the light source and the silicon substrate 7, and is a reflection film that reflects the SR light 1 emitted from the electron storage ring to the silicon substrate 7. . In this embodiment, the silicon substrate 7 has a single crystal structure. However, the same effect can be expected in both a polycrystalline structure and an amorphous structure as long as they are made of the same material. The reason why the material of the light-splitting member is a silicon film of the same material as that of the silicon substrate 7 is that light having a wavelength that causes damage to the substrate is absorbed by the light-splitting member, and reflected light radiated from the silicon mirror 5 to the silicon substrate 7. This is to prevent light having such a wavelength from being included.

Here, the light absorption of silicon corresponds to the binding energy of electrons in the atomic structure of silicon, and 8, 99, 149,
And light having a wavelength of 1800 eV. When a silicon compound is used for the mirror, the above binding energy is slightly shifted. Such a shift becomes larger as the energy becomes lower, such as 8, 99 eV, but when the high energy is used as the processing light source, the shift can be ignored. Specifically, the damage refers to damage such as lattice defects on the electrical characteristics (stability and reliability) of the semiconductor element when the silicon substrate 7 absorbs the light having the wavelength. When a transistor or the like is manufactured in a state where the silicon substrate has been damaged and instability between the thin film and the silicon substrate interface has occurred, carriers are trapped when carriers flow into such unstable portions, and the threshold voltage changes. In addition, the electrons gradually escape and the element characteristics also shift. As a result, stability over a long period of time is lacking, and operating reliability is reduced, such as a decrease in operating speed and a decrease in withstand voltage. In the present invention, since the light having the wavelength that causes such damage is removed by the silicon mirror 5 which is a spectral portion, damage to the substrate is reduced. The damage is reduced, for example, to such an extent that the threshold value hardly changes. In addition, since light having a wavelength absorbed by a gas required for CVD supplied by a gas introducing device 9 described later has a different bonding state from silicon, the light has a different electron binding energy and a different absorption wavelength. I do. Specifically, crystalline silicon has an absorption at 99 eV, but silicon film growth gas SiH ₄ has an absorption of 107 eV.
Shift to V. Therefore, even if the reflected light is used, the light can be efficiently decomposed.

The installation angle of the silicon mirror 5 in FIG. 1 is not limited to 45 °. If necessary, the angle of the silicon mirror 5 is adjusted by an angle adjuster or the like, so that the incident angle of light can be changed. As an example of the angle adjuster, an angle adjuster including a reflected light wavelength detector 11, a processing computer 12, and an angle adjusting means 13 of the silicon mirror 5 is provided. FIG. 2 shows a schematic diagram of such an angle adjuster. Here, the wavelength detector 11 and the angle adjusting means 13 are connected to the processing computer 12, and the angle adjusting means 13 has members 13a, 13b, 13c, and 13d. The processing computer 12 rotates the member 13a based on the data of the wavelength detector 11, and the rotation of the member 13c meshing with the member 13b on which the member 13a is mounted by this rotation rotates the member 13d which is mounted on the member 13c. The angle of the engaging silicon mirror 5 is adjusted. Thereby, the angle of incidence of the silicon mirror 5 is adjusted so that a predetermined wavelength is detected in the reflected light. Note that the angle adjuster may be of another method as long as the angle of the silicon mirror 5 can be adjusted. The angle adjustment may be performed in a direction perpendicular to that in FIG. By the way, the incident angle of the spectral member and the reflected light have the following relationship. That is, when the incident angle of the light-splitting member is changed, the wavelength of the reflected light changes. The more the incident angle is made obtuse, the stronger the light having a shorter wavelength is included in the reflected light. Conversely, the more the incident angle is made acute, the stronger the wavelength is included in the reflected light. That is, when the incident angle is increased, the ratio of the short wavelength component / the long wavelength component increases. Therefore, the optical excitation CV
While allowing for selectivity of excitation at D, it also allows for adjustment of substrate damage. In photoexcitation lithography, since exposure is performed using soft X-rays or the like having a short wavelength, it is necessary to make the incident angle obtuse than that of photoexcitation CVD.

The silicon film of the silicon mirror 5 has a thickness of about 7.8 mm to 1 cm, and is thick enough to absorb light having a wavelength at which the substrate is damaged. And silicon mirror 5
Is formed by polishing silicon to a mirror surface. It should be noted that the type of the silicon abrasive is not limited. If necessary, it is possible to move the reflection point so as to change it while keeping the incident angle constant. This is for improving the durability of the silicon mirror 5. FIG. 3 shows the silicon mirror 5
FIG. 2 shows a schematic diagram of a moving device that moves in the A ₁ and A ₂ directions. The moving device has a moving means 14 and a processing computer 15, and the moving means 14 has members 14a, 14b, 14c. Processing computer 1
The member 14a is rotated by 5 and the silicon mirror 5 is moved in the A ₁ and A ₂ directions by the member 14b meshing with the fixed member 14c. However, the moving method is silicon mirror 5
Any means can be used as long as it can be moved.

Further, the light-splitting member may be made of a mixture containing silicon or a silicon compound. For example, SiC or S
iN and the like are conceivable.

The spectral member is not limited to the reflection film. For example, the sample may be irradiated with light from a light source via a spectral member which is a transmission film of a compound containing substantially the same element as or a main constituent element of the substrate. That is, in the case of a silicon substrate, a silicon permeable film can be provided as a spectral member. The silicon permeable film must be thin enough to transmit light, for example, a thin film structure of about 1 mm. It goes without saying that the spectral members can be combined with each other, such as by combining the transmission film and the reflection film.

Further, the light separating member is not limited to a solid. For example, a chamber in which a silicon compound is gasified may be provided between the light source and the substrate. Examples of such gaseous silicon compounds include SiH ₄ , Si ₂ H ₆ , SiCl ₄ , and SiF ₄ . In addition, the object of the present invention is not lost even if the light-splitting member is formed of a liquid.

A differential pressure maintaining device 8 is provided between the vacuum chamber 4 and the flange 3b. The differential pressure maintaining device 8 has a function of maintaining the vacuum difference between the vacuum chamber 4 and the growth chamber 6 and transmitting the reflected SR light 1. Specifically, a differential exhaust device is generally provided with a slit through which light passes, and exhausting air between the slits.

The growth chamber 6 is a room for introducing a reaction gas from the gas introduction device 9 to grow a thin film on the silicon substrate 7.
The growth conditions are, for example, a reaction gas pressure of 0.1 to 1 Torr,
By setting the substrate temperature at 0 to 500 ° C., it is possible to deposit amorphous silicon. SiH ₄ , Si ₂ H ₆ or the like is used as the introduced gas. Gases unnecessary for thin film growth are exhausted by the exhaust device 10.

The present invention can be applied to other photoexcitation processing methods other than photoexcitation CVD, and is not limited to a semiconductor processing method.

〔The invention's effect〕

As described above, according to the present invention, a sample can be subjected to an optical excitation method without damaging a substrate in a semiconductor processing method or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part of a device for photoexcited growth of silicon by SR light 1 according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an angle adjuster, and FIG. 3 is a schematic diagram of a moving device. In the figure, 1 is SR light, 2 is a beam line, 3a and 3b are flanges, 4 is a vacuum chamber, 5 is a silicon mirror, 6 is a growth chamber, 7 is a silicon substrate, 8 is a differential pressure maintaining device, and 9 is gas introduction. The device, 10 is an exhaust device, 11 is a wavelength detector, 12 is a processing computer, 13 is an angle detector, 14 is a moving means, and 15 is a processing computer.

Claims (5)

(57) [Claims] 1. A light excitation processing method for irradiating a substrate (7) with light (1) from a light source via a light separating member (5) and performing a predetermined processing, wherein the light separating member (5) is provided on the substrate (5). A photoexcitation treatment method, wherein the same material as in (7) or a compound containing a composition element of the substrate is used. 2. The device according to claim 1, wherein the light-splitting member is a reflection film for reflecting the light from the light source from the light source to the substrate. Light excitation treatment method. 3. The photoexcitation processing method according to claim 1, wherein the light separating member is formed as a transmission film that transmits the light from the substrate and the light source. 4. The light excitation processing method according to claim 1, wherein the angle of the light separating member is adjustable. 5. A light excitation processing method according to claim 1, wherein said dispersing member is made of a gas or a liquid.