TW503502B - Method for examining whether the ion beam is orthogonal to the wafer surface - Google Patents

Abstract

This invention is related to a method for examining whether the ion beam is orthogonal to the wafer surface. A color-displaying layer and a etchable layer is formed sequentially on a wafer, and then a plurality of opening for exposing the color-displaying layer is formed in the etchable layer. After implanting to the color-displaying layer, the implanted areas will express a different color to the non-implanted areas. By said method, it is efficiently for verifying implanted and non-implanted regions on a wafer, and thus arriving the object for examining whether the ion beam is orthogonal to the wafer surface.

Description

V. Description of the invention (1)--5-1 Field of the invention: The present invention relates to an ion beam inspection method, and particularly to a method for inspecting whether an ion beam is perpendicular to a wafer surface. 5-2 Background of the Invention:. The application of ion implantation to semiconductor production dates back to about 1965 AD. After many years of research and development, "the current ion implantation technology can not only provide a variety of semiconductor doping = process requirements", but also can accurately control the doped man-made cover cloth. Therefore, it has become a VLSI. (VeryLarge Scale

Integration; the most important dopant presetting technology in the manufacturing process. In order to make the implanted ion beam (ion beam) have a more uniform momentum, generally a 'will be installed in the implanter (implanter) with a set of angle correction function (angle corrector) . This allows the ion beam to be implanted with a minimum range of incidence angles. However, in the actual operation of ion implantation, whether or not an angle corrector is installed, the position of the ion beam emitted from the implanter is usually set at the center of the wafer. This is because during ion implantation,

503502 V. Description of the invention (2) Except for the area perpendicular to the wafer surface (incident angle is 0 °), there is a set of incident angles between the ion beam and the wafer. Generally speaking, the closer to the center position of the surface of the wafer, the smaller the incident angle (even 0 °) between the implanted ion beam and the surface of the wafer. Conversely, the further away from the center position of the wafer surface, the larger the incident angle between the implanted ion beam and the wafer surface. For example, for a 6-pair wafer, when the ion implantation is performed, the incident angle of the ion beam and the wafer surface near the center of the wafer surface is 0 °, but at the edge of the wafer, The incident angle of the ion beam and the wafer surface may be as high as 3 °. Since the above-mentioned incident angle will have no effect on the implantation efficiency of doped ions, the conductivity (c ο n d u c t i v i t y) of the wafer may be changed. Therefore, in the process of ion implantation, it is an important subject to know the incidence angle of the ion beam in various regions on the wafer. In the conventional art, a heat ripple method (t h e r m a 1 w a v e) is often used to estimate the incident angle of the ion beam. The above method uses the change in refractive index to calculate the value of the incident angle. First, the correction curves of the relative relationship between the incident angle and the refractive index change are made by using various refractions formed by He / Ar rays projected on a group of test wafers at different incident angles. Next, after the ion implantation, for each ion implanted area, measure the change in the He / Ar refractive index, use the above-mentioned calibration curve, and add mathematical interpolation to calculate the measured area. Incidence angle of the ion beam 0

503502 V. Description of the invention (3) Although the above method can obtain the required angle of incidence of the ion beam, it is very tedious and difficult in actual operation, because a set of accurate calibration curves must be obtained first, and each The ion implantation area measures its refractive index one by one. It is undoubtedly a heavy and inconvenient task for the entire wafer process. Therefore, in order to perform ion implantation more efficiently and to estimate the results of ion implantation in a short time, it is urgent to find a simpler method to check whether the ion beam is perpendicular to the wafer surface. 5-3 Objects and Summary of the Invention: In view of the above-mentioned backgrounds of the invention, the conventional art has a number of disadvantages in checking whether the ion beam is perpendicular to the surface of the wafer. The main object of the present invention is to compare the color change of the color rendering layer to Provides a simpler way to check if the ion beam is perpendicular to the wafer surface. Another object of the present invention is that the method of the present invention can check whether the ion beams emitted from the ion implanter are parallel by comparing the color change of the color developing layer. According to the above-mentioned object, the present invention provides a method for checking whether an ion beam is perpendicular to a wafer surface. Sequentially formed on a wafer

503502 V. Description of the invention (4) A set of color-developing layer and a layer of engravable layer, and then removing a part of the above-mentioned etchable layer to form a plurality of openings to expose part of the above-mentioned color-developing layer. Due to the limitation of the thickness of the etchable layer and the width of the opening, the incident angle of the ion beam used for ion implantation must be within a certain range to successfully complete the ion implantation. More preferably, after the above-mentioned color-developing layer has undergone the ion implantation step, the area where the ion implantation is performed will show a different color from the area where the ion implantation is not performed. In this way, the method described above can be used to determine whether each area of the wafer surface has been implanted with ions, thereby achieving the purpose of checking whether the ion beam is perpendicular to the wafer surface. As for the sensitivity of the method of the present invention to the angle of incidence of the ion beam in terms of tilt, φ, the mathematical arc arc function (arc) can be used to calculate the ratio between the height of the etchable layer and the width of the opening formed. tangent; tan -1). 5-4 Detailed Description of the Invention: Some embodiments of the present invention will be described in detail as follows. However, in addition to the detailed description, the present invention can also be widely implemented in other embodiments, and the scope of the present invention is not limited, which is subject to the scope of subsequent patents. The three most important factors affecting ion implantation are energy, dose (d0 s e), and tilt angle (t i 11). In the present invention, studies are mainly made on the tilt angle.

503502 V. Description of the invention (5) A preferred embodiment of the present invention is a method for checking whether an ion beam is perpendicular to the surface of a wafer. First, a set of color developing layers and an etchable layer are formed on a set of test wafers in order. Next, a part of the etchable layer is removed to form a complex array opening to expose the color developing layer. After ion implantation is performed on the exposed color-developing layer, a color change will occur in the color-developing layer depending on whether or not the ion-implantation is performed. Then, the etchable layer is removed to facilitate analysis of the color change of the color developing layer. As for the sensitivity of the above method to the inclination of the incident angle of the ion beam, the mathematical arc arc function (arctangent; tan- 1) It is obtained by conversion. In order to more specifically illustrate the possible applications of the present invention, another preferred embodiment of the present invention is a method for checking whether an ion beam is perpendicular to a wafer surface. First, as shown in the first figure, a silicon oxide layer 1 1 0 is formed on the substrate 100 of a set of test wafers, and then a polycrystalline silicon layer 1 2 is formed on the silicon oxide layer 1 1 0 described above. 0. The above-mentioned silicon oxide layer 110 can be formed by some common methods. For example, a layer of silicon oxide is formed on the substrate 100 by a thermal oxidation method or a chemical deposition method. And the above-mentioned polycrystalline silicon layer 120 can also be formed by a common method. For example, a layer of polycrystalline silicon is deposited on the above-mentioned silicon oxide layer 1 1 0 by a chemical deposition method.

503502 V. Description of the invention (6) One of the key points of the present invention is the color developing layer 1 15 formed by combining the above-mentioned silicon oxide layer 110 and the polycrystalline silicon layer 120. Its main purpose is to provide color differences before and after the ion implantation process. Therefore, as long as it is a combination of one or more layers that can have a color difference before and after the ion implantation process, it can be used as the color developing layer 115 of the present invention, and is not limited to the silicon oxide layer and polycrystalline silicon in this embodiment. Combination of layers. A combination of a silicon oxide layer 110 having a thickness of about 300 angstroms and a polycrystalline silicon layer 12 having a thickness of about 800 angstroms will appear blue before the ion implantation process. What's more, after the ion implantation process, the area that is implanted with the ion will change color, and the area that is not implanted with the ion will maintain the original blue color. In this way, after undergoing the ion implantation process, it will be possible to easily determine whether a certain area has been implanted with ion by the obvious color change on the comparison wafer. Next, a etchable layer 130 is formed on the polycrystalline stone layer 120, and a part of the etchable layer 130 is removed to form a number of openings, and the polycrystalline silicon layer 12 is exposed, such as As shown in the second figure. The etchable layer 130 in the present invention should have a significant etching selection ratio with the polycrystalline silicon layer 120. In other words, in the subsequent etching process, only the etchable layer 130 will be removed without affecting the surface of the above polycrystalline silicon layer 120 and the color it presents, and thus the polycrystalline silicon layer 1 2 0 can be maintained Surface integrity. In actual operation, the above-mentioned etchable layer 130 may be a layer of nitrided stone formed by a method such as low pressure chemical deposition (LPCVD) or plasma chemical deposition (PECVD), or a layer of oxidized stone. Floor.

Page 10 503502 V. Description of the invention (7) Next, the above-mentioned polycrystalline silicon layer 12 is ion implanted. At this time, if the incident direction of the ion beam used is perpendicular to the surface of the polycrystalline silicon layer 120, the implanted ion beam will not be hindered by the etchable layer 130. In other words, the used ion beam can smoothly reach the area exposed by the polycrystalline silicon layer 12 in the opening of the etchable layer 130, complete the ion implantation, and form an ion implantation area 1440, as described in As shown in Figure A. On the other hand, if the incident direction B of the used ion beam is not perpendicular to the surface of the polycrystalline silicon layer 12 as shown in FIG. 3b, the implanted ion beam cannot reach the polycrystalline silicon layer 12 smoothly. 0 is exposed in the area of the above-mentioned etchable layer ί 30. That is to say, before the ion beam used reaches the exposed area of the polycrystalline stone layer 120, a part, or even all, of the ion beam is hindered by the above-mentioned etchable layer 130. As for ion implantation. After the ion implantation step is completed, the etchable layer 130 is removed, for example, by chemical mechanical polishing (CMP) or the like to remove the etchable layer 130, and then The polycrystalline silicon layer 12 in the color developing layer 115 was analyzed. As mentioned above, in this embodiment, the above-mentioned silicon oxide layer 1 and 10 and the polycrystalline silicon layer 1 2 0 _ appear a blue color before ion implantation. And after ion implantation, if there are areas that have undergone ion implantation, they will show different colors. For example, in this embodiment, the ions used for implantation are arsenic (As) ′, and if there is a region in the color rendering layer 115 that has been implanted with arsenic ions,

503502 V. Description of the invention (8) The color will change from blue to off-white. In this way, by comparing the color changes on the color rendering layer 115, it will be helpful to determine whether a certain area has been subjected to ion implantation. Furthermore, in the method of the present invention, the sensitivity for checking whether the ion beam is perpendicular to the surface of the wafer can be obtained by a simple mathematical calculation program. In the above embodiment, if the thickness of the etchable layer 130 is Η, and the width of the opening formed in the etchable layer 130 is W, as shown in the second figure, it is used. The incident angle of the ion beam is $, as shown in the third B figure. Then the relationship can be expressed by the tangent function (tangent; tan) in the trigonometric function, as shown in the first formula. tanO = (W / H) (Formula 丨 Therefore, 'The sensitivity of the present invention to the inspection of whether the ion beam is perpendicular to the wafer surface can be obtained by a simple conversion. θ = tan_1 (W / H) (Second formula) 2. After the operation of an inverse trigonometric function, convert the above tangent function into an inverse tangent function (arc hngent; tarr1) to calculate the above-mentioned ion beam ^ radiation angle Θ. In other words, the used ion beam reaches the wafer surface _ If If the incident angle is larger than the value obtained from the second formula above, 1 ^ can be accurately detected by the method of the present invention. Therefore, if the two Z increases the thickness of the engravable layer and reduces the opening Width to help improve the present invention. For checking whether the ion beam is perpendicular to the wafer surface

Page 12 503502 5. The sensitivity of the invention (9). On the other hand, there is currently no simple inspection method that can be used to check whether the angle corrector used in an ion implanter, or a similar device used to focus an ion beam, has a normal focusing effect. The method of the present invention can be used to check the implantation condition on the wafer as described above, and can also be used as a method for inspecting the aggregation effect of the aggregation device in the ion implanter. By the method described above, by observing and comparing the change in the implantation range of the ion beam on the wafer, it can be known whether the ion implanter used has changed in the focusing effect. To sum up, the present invention determines the ion implantation situation on the wafer surface by the color change on the wafer before and after the ion implantation step, thereby achieving the purpose of checking whether the ion beam is perpendicular to the wafer surface. Therefore, the present invention can provide a simple method for checking whether the ion beam is perpendicular to the wafer surface. The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of patent application of the present invention; Equivalent changes or modifications made under the spirit of the disclosure should be included in the scope of patent applications mentioned below.

The 503502 diagram on page 13 briefly illustrates the above-mentioned objects and advantages of the present invention. The following embodiments and diagrams will be used to explain in detail as follows, wherein: the first diagram, the second diagram, the third A diagram, and the third B diagram It is a schematic structural diagram of each step when performing ion implantation on a wafer according to the technology disclosed in the present invention. Representative symbols of the main parts: I 0 0 substrate II 0 silicon oxide layer 115 color rendering layer 12 0 polycrystalline silicon layer 1 3 0 etchable layer, 1 4 0 ion implantation area A ion beam incident direction perpendicular to the wafer surface B not The incident direction of the ion beam perpendicular to the wafer surface Θ the incident angle of the ion beam

Page 14

Claims (1)

503502 6. Scope of patent application 1. A method for checking whether an ion beam is perpendicular to a wafer surface, comprising: providing a wafer, the wafer is covered by a color developing layer; forming an etchable layer on the color developing layer; Removing the etchable layer to expose the color developing layer; performing ion implantation to the exposed color developing layer; and In terms of analysis, the gradation of the carved layer #color can be displayed. Hai Hai = mouth = mouth. The narrative of the change is colored in color, and the present party presents the first step of the previous step after the first inspection. The brother ’s enrollment Fan Zhilizi leaves, please apply for the application as the 2 In the description of the layer color > 〇 Method and above •, check the silicon oxygen of the silicon wafer in the layer check. The 1 will be committed in the first layer: the oxygen-containing package of the crystal one by one. The inspection method according to item 1 of the scope of patent application, wherein the color-developing layer is composed of a silicon oxide layer having a thickness of about 300 angstroms and a polycrystalline silicon layer having a thickness of about 800 angstroms. 5. The inspection method according to item 4 of the scope of patent application, wherein the color-developing layer is blue. 6. The inspection method according to item 1 of the scope of patent application, wherein the above-mentioned etchable Page 15 503502 6. Scope of patent application The layer is a nitrided layer. 7. The inspection method according to item 1 of the scope of the patent application, wherein the above-mentioned engravable layer is a monoxide layer. 8. The inspection method according to item 1 of the scope of patent application, wherein the analysis step of the color developing layer is to compare the color of one ion-implanted region in the color developing layer with the other color of an ion-implanted region. 9. The inspection method according to item 1 of the scope of patent application, wherein the analysis step of the color developing layer 0 includes at least a ratio of a thickness of the etchable layer to a width of the exposed color developing layer. Step of ion beam deviation angle. 10. A method for checking whether an ion beam is perpendicular to a wafer surface, comprising: providing a wafer, the wafer being covered by a color-developing layer; forming an etchable layer on the color-developing layer; removing a part of the Etching the layer to form a plurality of openings that can expose the color developing layer; performing ion implantation to the exposed color developing layer; removing the etchable layer; and analyzing the color developing layer. Π. The inspection method of item 10 in the scope of patent application, wherein the above-mentioned color development Page 16 503502 6. Scope of patent application The layer can show color changes before and after the ion implantation step. The method of color display is described above. Fang and Shangcha •, the slice of silicon on the layer g g BB oxygen 1 should be based on the surrounding layer layer: ^ 7 ^ Containing chemical crystals to cover more oxygen, please apply step by step, such as forming a sinking shape 2 1 3. The inspection method according to item 10 of the scope of patent application, wherein the color rendering layer is composed of a silicon oxide layer having a thickness of about 300 angstroms and a polycrystalline silicon layer having a thickness of about 800 angstroms. composition. 14. The inspection method according to item 13 of the scope of patent application, wherein the above-mentioned color-developing layer is blue. 15. The inspection method according to item 10 of the scope of patent application, wherein the etchable layer is a nitrided layer. 16. The inspection method according to item 10 of the scope of patent application, wherein the above-mentioned etchable layer is a monolithic oxide layer. 1 7. The inspection method according to item 10 of the scope of patent application, wherein the color analysis layer analysis step described above compares the color of one ion-implanted region of the color-developed layer with another color of an ion-implanted region. . Page 17 503502 6. Application for Patent Scope 18 • The inspection method for item 10 of the scope of patent application, wherein the above-mentioned color analysis layer analysis step includes at least one utilizing the thickness of the etchable layer and the exposed color development. The step of calculating the deviation angle of the ion beam by the ratio of the width of one layer. 19. A method for checking whether an ion beam is perpendicular to a wafer surface, comprising: depositing a silicon oxide layer on a wafer; depositing a polycrystalline silicon layer on the silicon oxide layer; depositing a etchable layer on the polycrystalline silicon layer Etching the etchable layer to form a plurality of openings that can expose the polycrystalline silicon layer; ion implantation into the polycrystalline silicon layer; removing the etchable layer; and performing the polycrystalline silicon layer analysis. 20. The inspection method according to item 19 of the scope of patent application, wherein the color-developing layer can exhibit a color change before and after the ion implantation step. 2 1. The inspection method according to item 19 of the scope of patent application, wherein the etchable layer is a nitrided layer. Xin 2 2. The inspection method according to item 19 of the scope of patent application, wherein the above-mentioned etchable layer is an oxide cut layer. Page 18 503502 6. Application for Patent Scope 2 3. The inspection method for item 19 of the scope of patent application, wherein the above-mentioned polycrystalline silicon layer analysis step is compared to an ion implantation area of the combination of the silicon oxide layer and the polycrystalline silicon layer. And another color of an area without ion implantation Page 19