JPH0746688B2 - Surface treatment method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for etching a solid surface using light, and more particularly to an etching method suitable for lowering the temperature of a semiconductor process.

[Background of the Invention]

As the integration of semiconductor devices progresses, lowering the manufacturing process temperature is becoming a major technical issue. Etching methods currently used in actual processes include liquid-phase food methods and plasma etching methods. In the former, the substrate temperature is kept low, but it is difficult to control the etching reaction temporally and spatially, so it is difficult to precisely adjust the etching amount and avoid side etching, and it is difficult to perform fine processing. Inadequate as a means. Furthermore, since this method is a wet process, it is also a factor that complicates the process. On the other hand, the plasma etching method is a dry process, and is superior to the above liquid phase etching method in that it can give anisotropy to the etching reaction to some extent. However, in the case of this method, damage to the substrate due to ions and high-speed particles in the plasma is unavoidable, and there is also the drawback that the substrate temperature rises to about 800 ° C during processing, and from the viewpoint of lowering the process temperature. Is not a satisfactory method.

At present, a vapor-phase etching method using light is attracting attention as a means for solving the above-mentioned problems of the etching method adopted in the actual process.
In this method, a gas that activates the etching action only when irradiated with light having a specific wavelength is used as the etching agent. In some cases, a method is used in which the activation of the etching action works effectively only in the light-irradiated portion of the substrate.
With respect to such a vapor-phase etching method using light, various examples have been reported in combination of a substrate material, a gas serving as an etching agent, a light source used for light irradiation and an irradiation method. For typical examples, see TJ Chuang, Journ
al of Vacuum Science Technology, 21 , 798 (1982) and Surface Science Reports by the same author, 3 , 1 (198).
It is summarized in the table on page 78 of 3). Such a vapor-phase etching method using light has the advantages that the substrate can be kept at a low temperature, the surface is not damaged, and a fine pattern can be formed. Since the wavelength of light that can be used to advance the etching reaction varies depending on the combination of gases that are the etchant, if only a light source that covers a limited wavelength range can be used,
There is a drawback in that the substrate materials that can be used in this method are limited in type.

[Object of the Invention]

An object of the present invention is to provide a surface treatment method which solves the above problems.

[Outline of Invention]

In order to achieve the above object, in the present invention, a gas phase etching reaction by orbital radiation is used. The orbital radiant light is a continuous light that covers a wide wavelength range from X-rays to visible light, which is a remarkable feature that does not exist in light obtained from conventional light sources. It is an effective means for avoiding the drawbacks of the vapor phase etching method. The method according to the present invention is an application of a photochemical reaction. In general, the wavelength region of light required for efficiently proceeding a photochemical reaction differs depending on the target substance. This wavelength region is often the ultraviolet region or a region shorter than the ultraviolet region, but a continuous light source that can sufficiently cover such a wavelength region has not existed before the advent of orbital radiation. Therefore, the above-mentioned characteristics of orbital synchrotron radiation are extremely advantageous for realizing new technical means for applying photochemical reactions including the method of the present invention.

The gist of the present invention is as follows: (1) Orbital radiation is applied to the surface of the object to be processed without supplying a reaction gas for etching the surface of the object placed in the processing chamber to the surface of the object to be processed. Following the step of removing impurities on the surface of the object to be processed by irradiation, and (2) following the step (1), the orbital radiation while supplying the reaction gas to the surface of the object to be processed in the processing chamber. And a step of etching the surface of the object to be processed by irradiating with light, the surface treatment method.

Example of Invention

FIG. 1 is a conceptual diagram showing an example of the structure of an apparatus necessary for carrying out the present invention. This device includes a light source unit A, a light selection unit B,
It is composed of a processing unit C. The light source unit A has an electron synchrotron or an electron storage ring as a main component,
It has a function of producing orbital radiation necessary for carrying out the present invention and guiding the orbital radiation to the light selecting section B. Light selector B
In, in the orbital radiated light guided from the light source unit A,
The required light of a single wavelength range or a plurality of wavelength ranges is extracted and sent to the processing section C. In addition, the light selection section B is
It also has a function of controlling the time and timing of the light sent to the processing section C as necessary. The light selecting section B has optical elements such as a diffraction grating and a mirror as main constituent elements, and various filters and shutters are attached thereto. These elements are controlled so that light having the necessary conditions can be supplied to the processing section C. The function required of the light selecting section B is to process and control the orbital radiation emitted from the light source section A,
After being converted into orbital radiant light having necessary conditions, it is sent to the processing section C. If you have this feature,
As the light selection unit B, it is possible to use a device having a configuration different from that of the above embodiment. The processing section C has a processing chamber for etching a substrate as a main constituent element. This processing chamber is an auxiliary device, which is a mechanism for adjusting a gas serving as an etching agent, a mechanism for introducing the gas into the processing chamber, a mechanism for transporting and aligning a substrate for processing, a mask for transferring a pattern to the substrate, And a mechanism for fixing it at a predetermined position, the light selection section B
It is equipped with an optical system and the like for adjusting the light sent from the device to the required shape and direction. The accessory device has a function of making the irradiation light amount uniform on each part of the substrate or the mask. It is also possible to add a function of performing continuous or parallel processing of a plurality of substrates or a function of performing processing with a plurality of masks to the accessory device. The light selection unit B and the optical system provided in the processing unit C can irradiate the substrate with light in a plurality of wavelength ranges simultaneously or at desired timing while controlling the direction and region. Of course, it is also possible to irradiate the substrate with light of a single wavelength range while performing the same control as above. When the light to be used has a single wavelength range and it is not necessary to select the light in the specific wavelength range among the lights generated in the light source section A, the light selecting section B sends the light to the processing section C. It suffices if it has a function of controlling time and timing. The light source unit A, the light selection unit B, and the processing unit C are provided with independent vacuum exhaust systems, and the light source unit A and the light selection unit B are provided by a differential exhaust system or an optical path having a light transmissive window. Further, the light selecting section B and the processing section C are connected.

FIG. 2 is a conceptual diagram showing an example of processing steps using the above apparatus. First, the substrate 1 is irradiated with orbital radiation 2 in a processing chamber kept in a vacuum. As a result, the impurities adsorbed on the surface of the substrate 1 are removed from the surface by the photoinduced desorption process, and the surface of the substrate 1 becomes clean. Here, as the orbital radiated light 2, not only one having a single wavelength range but also one having a plurality of wavelength ranges may be used simultaneously or sequentially. As the wavelength range of the orbital radiated light 2, for example, a range in which the shell electrons of the constituent elements of the impurities existing on the surface can be excited is used. Next, the mask 3 on which a predetermined pattern is drawn is placed at a position where the pattern can be transferred to the surface of the substrate 1, a gas 4 serving as an etching agent is introduced into the sample chamber, and then light 5 and 6 are irradiated. To do. Of course, it is also possible to use the substrate 1 whose non-etched portion is protected by a resist film. In this case, it is not necessary to use the mask 3. Here, the role of the irradiation light 5 and 6 is to promote the etching reaction on the substrate 1. Therefore, it is not always necessary to simultaneously irradiate two kinds of orbital radiations 5 and 6 as shown in FIG. 2, but the conditions such as the material of the substrate 1 and the composition with the gas 4 serving as an etching agent. Depending on the, various irradiation methods are used. For example, after irradiating the orbit synchrotron radiation of single or plural wavelength ranges for a certain period of time, and then irradiating the orbit synchrotron radiation of another single or plural wavelength ranges for a certain period of time, or repeating this operation a plurality of times. In some cases, different irradiation methods are used. In such an irradiation method, for example, since the reaction between the substrate material and the gas 4 serving as the etching agent proceeds, the substrate 1
In the case where both the gas and the gas 4 serving as an etching agent need to be photoexcited, and the reaction product generated on the substrate 1 as a result of this reaction becomes volatile only when photoexcited, the substrate Suitable wavelength range for photoexcitation of material (
a), a wavelength range suitable for photoexcitation of the gas 4 serving as an etching agent (this is λb), and a wavelength range convenient for photoexcitation of the reaction product (this is λc). Available if there is no match. As a light irradiation method in such a case, for example, first, light having a wavelength range of λa and λb is simultaneously irradiated for a certain time, and then light having a wavelength range of λc is irradiated for a certain time, or this operation is repeated a plurality of times. There are ways to do it. As described above, by adjusting the conditions such as the wavelength range of the orbital radiated light to be irradiated, the irradiation time, and the irradiation timing according to the material of the substrate 1 and the composition of the gas 4 serving as an etching agent, many materials can be obtained. A desired etching pattern can be formed on the substrate 1.

As described above, according to this embodiment, it is possible to perform processing based on various photochemical reactions in the same apparatus, so that it is possible to form etching patterns on substrates of various materials at low temperatures. . Further, according to the present embodiment using the orbital radiation light, it is not necessary to use a plurality of light sources together even when light in a plurality of wavelength ranges is used at the same time. Therefore, even when etching is performed by using the conventional light source, the efficiency of the processing can be improved by using this embodiment.

〔The invention's effect〕

According to the present invention, since it is not necessary to expose the object to be processed to the atmosphere after cleaning the surface of the object to be processed, the clean surface of the object to be processed can be etched. Further, since the impurity removing process and the subsequent etching process can be performed in the same apparatus, the throughput can be improved by using the present invention in mass production of semiconductor devices, for example.

[Brief description of drawings]

FIG. 1 is a conceptual view for explaining an embodiment of an apparatus for carrying out the method according to the present invention, and FIG. 2 is a view for explaining an embodiment of a treatment step according to the method of the present invention. A ... Light source section, B ... Light selection section, C ... Processing section, 1 ... Substrate, 2,
5, 6 ... Irradiation light, 3 ... Mask, 4 ... Gas that serves as an etching agent.

Claims (2)

[Claims] 1. A surface treatment method comprising the following steps. (1) Irradiating the surface of the object to be processed with orbital radiation without supplying a reaction gas for etching the surface of the object to be processed placed in the processing chamber to the object to be processed. A step of removing impurities on the surface of the processed material. (2) Subsequent to the step (1), a step of etching the surface of the object to be processed by irradiating the surface of the object to be processed in the processing chamber with the orbital radiation while supplying the reaction gas. 2. The surface of the object to be processed is irradiated with the orbital radiation through a patterned mask provided on the surface of the object to be processed in the step (2). The surface treatment method according to claim 1.