JPS62254423A - Semiconductor printing device - Google Patents

Abstract

PURPOSE:To miniaturize a semiconductor printing device by providing an alignment observation optical system, which has a peculiar position reference and is capable of observation of a mask pattern surface before arrangement of a wafer and a mark or a pattern previously formed on the rear of a wafer after the arrangement of the wafer, on the rear side of the wafer. CONSTITUTION:While using alignment observation optical sytems 5a and 5b, a mask holder on a frame 3 is moved by a moving mechanism so that patterns 2a and 2b for positioning a mask 2 might be in accordance with reference marks within the view fields of said optical systems 5a and 5b, thereby positioning the mask. After that, a wafer 1 held by a wafer chuck 4 is placed right under the mask and the chuck 4 is moved by a stage or the like so that alignment marks 1a and 1b on the rear of the wafer might be in accordance with the reference marks of the alignment observation optical systems 5a and 5b and thus the positioning of the mask is done. Subsequently, a pattern of the mask 2 is printed on a surface resist layer by irradiation with the light from an exposure light source 6. Thus, a high-accuracy alignment can be attained by means of a simple and small-sized constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor printing apparatus that places a mask on the back side of a wafer coated with resist and transfers a mask pattern onto the back side of the wafer.

[Prior Art] Traditionally, in the manufacture of ICs, LSIs, etc., various photomasks have been applied after applying photoresist to the back surface of the wafer in order to diffuse impurities into desired areas of the wafer or to provide wiring. The mask pattern is exposed and transferred through the wafer, followed by development and etching. This process is repeated several times during the series of manufacturing steps, but for the second and subsequent exposures, the pattern to be printed next is aligned in a predetermined positional relationship with respect to the pattern that has already been printed. Then, exposure and etching are performed.

This process of alignment, exposure, and etching is performed only on one side of the square in normal semiconductor circuits, but in the case of thyristors, triacs, crystal resonators, etc., due to the necessity of the process due to their structure, photo etching is performed. is performed on both sides. Therefore, mutual alignment of patterns must be performed not only between patterns on the same side, but also between a pattern printed on one side and a pattern to be printed on the opposite side.

As a method for printing mutually aligned patterns on both sides of a square, for example, Japanese Patent Application Laid-Open No. 17973/1983 discloses a method (hereinafter referred to as method A) in which patterns are simultaneously printed on both sides of a square. There is.

Another method that has been considered is a method in which two masks, each with a pattern to be printed, are aligned with each other in advance, and the pattern is printed with a square sandwiched between them (hereinafter referred to as method B). , or observation optical system on both sides respectively.

There is a method in which images obtained from both observation optical systems are formed within the same field of view by some optical means, and the images are aligned and printed (hereinafter referred to as method C). Use the wafer back side to the wafer back side.
There is a method (hereinafter referred to as "method") in which the pattern on the surface is observed, the front and back patterns are aligned, and then printed.

However, method A has the drawback that the exposure optical systems must be placed on both sides of the wafer, which inevitably increases the size of the apparatus.

Furthermore, in method B, after aligning the respective masks with each other, the gap between both masks is widened without shifting the relative positions of both masks, the square is positioned between both masks, and the gap is narrowed again. Not only does this make the mechanism complicated, but the exposure optical system must be placed on both sides of the wafer, or if a single exposure optical system is used, the two mask surfaces must be placed on the back side with the wafer sandwiched between them. This method requires a mechanism to repeatedly rotate the device, which has the disadvantage that the device inevitably becomes larger or more complicated.

Furthermore, in method C, the accuracy of the optical system that guides images from both observation optical systems into the same field of view directly affects the alignment accuracy, so there is a drawback that it is difficult to manufacture and adjust the optical system.

Furthermore, the above method has the disadvantage that alignment is difficult because the observed image is unclear.

Note that the above is a conventional technique for printing patterns on both sides of a square panel, but even when printing an actual element pattern on only one side of a square panel, conventionally there are no steps during the series of semiconductor device manufacturing processes. It may be necessary to recreate the alignment marks every time, or part or all of the alignment pattern may be missing during the etching or epitaxial process, making subsequent alignment impossible.Furthermore, the resist applied to print the pattern may cause alignment problems. It is true that there have been disadvantages such as a decrease in alignment accuracy due to light diffraction, absorption, reflection, or interference.

[Problems to be Solved by the Invention] An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods and to easily miniaturize the structure for printing mutually aligned patterns on both sides of a wafer. Our goal is to provide a semiconductor printing device that enables high-precision alignment.
At the same time, it is an object of the present invention to provide a semiconductor printing apparatus which does not cause the above-mentioned disadvantages even when a real element pattern is formed by printing only on one side of a square.

[Means for Solving the Problems] According to the present invention, the above-mentioned problems are unique to a semiconductor printing apparatus that places a mask on the back side of a wafer coated with a resist and transfers a mask pattern to the back side of the wafer. An alignment observation optical system is arranged on the back side of the wafer, which has a position reference and can observe the mask pattern surface before placing the wafer, and can observe marks or patterns previously formed on the back side of the wafer after placing the wafer. This is achieved through configuration.

[Function] In the present invention, an alignment observation optical system having a unique positional reference is placed on the back side of the square, and when the square is not arranged, the mask pattern surface is observed from the wafer side and the optical system is In addition to aligning the mask pattern with respect to the position reference set in the system, when the wafer is placed, the marks formed in advance on the back side of the wafer are observed and alignment is performed with respect to the position reference. It is something.

For example, when printing mutually aligned patterns on both sides of a sea urchin, the mask pattern is printed on one side of the wafer after the alignment observation optical system aligns the mask pattern with respect to the position reference set in the observation optical system. , thereby forming an alignment pattern corresponding to the mask pattern on one side of the wafer. Next, after aligning the same or different mask pattern with respect to the position reference set in the alignment observation optical system, the other side of the pattern is placed facing the mask side, and the pattern formed on the back surface of the wafer in the previous process is The alignment pattern thus obtained is captured by the alignment observation optical system, and the alignment pattern is aligned with respect to the position reference set in the observation optical system. In this case, the alignment pattern on the back side of the wafer is observed without resist applied to the back side of the wafer, and there is no risk of deterioration in alignment accuracy due to observation of the alignment pattern in the presence of a resist layer. Thereafter, pattern printing on both sides is repeated in the same manner, but the alignment of the back side of the wafer, which is the printing side, is performed based on the marks or patterns on the back side of the wafer formed in the previous process or the previous process.

If the actual device pattern is to be printed multiple times on only one side of the wafer, an alignment mark corresponding to the mask pattern is printed on one side of the wafer in the first baking process described above, and this side is then used as the back side of the wafer. Alignment is performed exclusively using the alignment mark on the back side. In this case, the alignment mark on the back surface of the wafer is not damaged during a series of semiconductor device manufacturing steps, and is not covered by the resist layer, so no inconvenience occurs.

In order to further understand the present invention, preferred embodiments of the present invention will be described below with reference to the drawings.

[Embodiment] FIG. 1 is a schematic cross-sectional view showing an example of the present invention, and FIG. 2 is a cross-sectional view of a state in which a square is not arranged.

In the figure, a reference frame 3 holds a photomask 2 on its upper surface, and the position of the photomask 2 can be adjusted on this frame 3 by a mask holder and a moving mechanism (not shown). The photomask 2 is placed on the frame 3 with its patterned surface facing downward, and only the alignment patterns 2a and 2b among the patterns are shown in the figure.

A wafer 1 held on a wafer chuck 4 is placed directly under the mask of the frame 3 so as to be able to enter and leave the frame 3, and the chuck 4 can be moved for positioning by slightly displacing the chuck 4 using a movement stage (not shown). ing.

The front surface of the wafer 1 is coated with resist, and alignment marks ta, tb are formed at predetermined positions on the back surface of the wafer 1.
is preformed.

The wafer chuck 4 holds the wafer 1 on its upper surface by suction or the like, and aligns the alignment mark l on the back surface of the wafer.
The portions corresponding to a and lb are hollow portions 4 penetrating in the thickness direction.
a and 4b, and the marks la and lb can be directly observed from the back side.

An exposure light source 6 and an exposure optical system (not shown) are arranged above the frame 3, and an alignment observation optical system 5a supported by the frame 3 is located on the opposite side of the light source 6 across the mask and the wafer, that is, on the back side of the wafer. , 5b are arranged.

The alignment observation optical systems 5a, 5b themselves have their own positional reference with respect to the frame 3, and have, for example, a reference position mark or scale within their observation field.

In the above configuration, first, as shown in FIG. 2, the mask patterns are aligned in a state where no squares are placed. That is, using the alignment observation optical systems 5a and 5b in the state shown in FIG. 2, the mask holder (not shown) on the frame 3 is placed so that the alignment patterns 2a and 2b of the mask 2 are aligned with the reference marks within the field of view. is moved by a moving mechanism to align the mask. After this, as shown in FIG. 1, the wafer 1 held by the wafer chuck 4 is positioned directly under the mask, and using the alignment observation optical systems 5a and 5b in the same state, the alignment mark 1a on the back surface of the wafer is aligned with the reference mark. , 1b are aligned with each other by moving the chuck 4 using a stage or the like, and aligning the chuck 4 with the square.

After the above alignment is completed, the exposure light source 6 is irradiated to print the pattern of the mask 2 onto the resist layer on the surface of the wafer 1.

If you want to print the actual device pattern multiple times only on the surface of the wafer 1, you can repeat the same baking process many times, and if you want to print patterns that are aligned with each other on both sides of the wafer 1, you can use the above-mentioned baking process. The marks (patterns) formed from the mask patterns 2a and 2b printed on the surface of the wafer 1 in the next step are used as alignment marks la and lb on the back side of the wafer to perform alignment when the wafer is turned over.
By repeating this process thereafter, a highly accurate double-sided matching pattern can be printed.

In this embodiment, a one-proximity type is used as an example for convenience of explanation, but the present invention is not limited to this, and various semiconductor printing apparatuses such as a contact type, a mirror projection type, or a step-and-repeat type are used. Applicable to

[Effects of the Invention] As described above, in the semiconductor printing apparatus of the present invention, the mask pattern is observed and aligned from the wafer side using an alignment observation optical system having a unique position reference, and the mask pattern is aligned on the wafer back surface. For pattern printing, the alignment mark or pattern on the backside of the wafer is observed and aligned from the backside of the wafer based on the same specific positional reference as above, and the exposure optical system and alignment observation optical system are each configured as a single unit. However, it is possible to print patterns that are aligned with each other on both sides of the wafer, there is no need to complicate the mechanism for loading and unloading the wafer, and the alignment marks on the wafer can be observed in areas where there is no resist layer, improving alignment accuracy. It is possible to achieve high precision alignment between both sides of the wafer with a small and simple configuration, and even when printing actual device patterns on only one side of the wafer, alignment marks can be formed once on the back side of the wafer. If so, the conventional inconveniences can be completely eliminated.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, and FIG. 2 is a similar sectional view in a state where no wafer is placed. 1: Wafer, la, lb: Alignment mark on back side of wafer 2: Photomask, 2a, 2b: Mask pattern for alignment, 3: Reference frame, 4: Wafer chuck, 4a, 4b: Hollow part, 5a, 5b: Alignment observation Optical system, 6: Exposure light source.

Claims (1)

[Claims] In semiconductor printing equipment that places a mask on the surface side of a wafer coated with resist and transfers the mask pattern to the wafer surface, it has a unique position reference and can observe the mask pattern surface before placing the wafer, and after placing the wafer. A semiconductor printing apparatus characterized in that an alignment observation optical system capable of observing marks or patterns previously formed on the back surface of the wafer is disposed on the back surface side of the wafer.