JPH0428099B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a projection exposure apparatus, and more particularly to an apparatus suitable for exposing a film strip. Photoetching is often used to form an IC lead frame on a strip-shaped metal film. Conventionally, the exposure device used for this means is
It is configured as conceptually shown in the figure. That is,
In this device, a metal film 1 coated with photoresist on both sides is sandwiched between square and annular printing frames 2 and 3 to form a flat surface perpendicular to the optical axis, and images of photomasks (not shown) for the front and back sides are captured at F ₁ Film 1 is passed through the lens at point F2 and the lens at point _F2 .
It is designed to expose an image on the top. Films used in such devices usually have holes 4 formed at regular intervals on both edges of the film 1, as shown in FIG. 2, and these holes 4 are used for positioning during exposure, driving the film, etc. . By the way, such a hole 4
is generally formed by press punching, but there are certain limits to the dimensional accuracy of the individual holes 4 and the accuracy of the hole spacing. Therefore, if the distance between the holes 4 is larger than the distance between the alignment pins 5 ₁ to 5 ₃ and 5 ₄ to 5 ₆ shown in FIG. When it is wrinkled, for example between pins 5 ₁ and 5 ₃ or 5 ₄ and 5 ₆ , it may take on a shape that bulges to one side as shown in FIG. When a film with poor flatness is exposed in this way, the image formation position shifts,
The image formation patterns on the front and back sides, which should originally match, do not match. If etching is performed if the patterns on the front and back sides do not match, the etched cross section will not be vertical, and as the pattern becomes finer, this defect becomes fatal. A trial calculation of the magnitude of this deviation using a model is as follows. In FIG. 4, point A is, for example, the center of pin 5 ₁ in FIG. 2, and point B is the center of pin 5 ₃ in the same manner. Now, suppose that the distance between the pins 5 ₁ and 5 ₃ is Lmm, and when the distance between the holes 4 corresponding to these pins is larger by ΔLmm, the film 1 curves approximately as APB. If the center of AB is O, then the overhanging distance ΔH at point P from point O is expressed by the following equation. (△H) ² + (L/2) ² = (L+△L/2) From ²

[Formula] Therefore, when exposing with a pattern to be imaged at point R on AB, which is r away from point O, the pattern on the F ₁ side will actually be imaged on Q ₁ , and the pattern on the F ₂ side will be imaged on Q ₂
image is formed. FIG. 5 shows an enlarged view of that part.
Then, the point where the perpendicular line passing through point R intersects with straight line PB is Q
Then, the distance Δh between QPs is expressed by the following equation. △h=△H・(1-2r/L) If the intersection points of perpendicular lines drawn from points Q ₁ and Q ₂ to straight line OB are R ₁ and R ₂ , then the deviation of points Q ₁ and Q ₂ from point Q is △ q ₁ and Δq ₂ are approximated to the deviations Δr ₁ and Δr ₂ from point R to points R ₁ and R ₂ , respectively, and their values can be approximated to Δr. This △r is obtained from the similarity of triangle F ₁ OR (F ₂ OR) and triangle Q ₁ R ₁ R (Q ₂ R ₂ R) in Figure 4. OF ₁ /r=Q ₁ R ₁ /△r ₁ ≒△h /△r Younger version becomes OF ₂ /r=Q ₂ R ₂ /△r ₂ ≒△h/△r, and △r=△h・r OF ₁ or △r=△h・r/OF ₂ . Therefore, for example, L = 40 mm, △L = 0.005 mm, OF ₁ (OF ₂ ) = 100
If mm, Δh=0.316 mm, and Δh and Δr are as follows for r values of 0, 5, 10, 15, and 20 mm.

[Table] The results are shown in Figure 6. In the figure, the horizontal axis is the position of point R, and the vertical axis is OR ₁ - OR or OR ₂ -
Indicates the value of OR (μ). From this figure, film 1 is
When deflecting like an APB, it can be seen that the positional deviation of the image formation increases once toward the periphery and then decreases. That is, according to the above calculation, the maximum deviation is r = 10
mm, it reaches about 30 microns. Therefore, if the line width of the pattern is 30 microns, if the imaging position is shifted by 30 microns, the cross section that should be shown in Figure 7A when etched will become the one shown in Figure 7B. It is clear that a normal etching product cannot be obtained. Moreover, the formation error of pin hole 4 used in the above calculation △L = 0.005 mm
is a small number; in reality, it can be up to several tens of microns. For this reason, there are restrictions on the positions where fine patterns can be formed, which has been a major obstacle in pattern design. In order to eliminate such conventional drawbacks, the present invention installs a flat plate arranged with a gap slightly larger than the thickness of the material to be exposed and larger than the exposed surface, and makes at least the exposed side transparent. The material to be exposed is sandwiched between flat plates and arranged perpendicular to the optical axis to form an imaging section, and the positional deviation of the imaging is minimized. An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 8 is a sectional view showing an embodiment of the imaging section in the projection exposure apparatus of the present invention. As shown in the figure,
In this imaging section, transparent flat plates 8 and 9, which are slightly larger than the exposure surface, are arranged so as to have a gap slightly larger than the thickness of the film 1 to be exposed, and to be perpendicular to the optical axis. The flat plates 8 and 9 are supported by printing frames 6 and 7, respectively, and the printing frame 7 is provided with a pin 5 for gap adjustment and exposure positioning.
If an imaging section having such a configuration is used in place of a conventional printing frame, it can be used in exactly the same manner as a conventional printing frame. Incidentally, the flat plates 8 and 9 may be made of any material as long as they are transparent, but glass is most preferable in terms of cost. Also,
The method of supporting the light-transmitting flat plate is not particularly limited, but it is preferable to make it removable since it is unavoidable that dust will adhere to it during repeated use. The gap between the two flat plates 8 and 9 needs to be at least larger than the thickness of the material to be exposed 1, but the preferred size of the gap is about 100 microns plus the thickness of the material to be exposed. In this way, the curvature of the exposed material can be corrected to a small degree, so ΔH becomes small, and therefore Δh and Δr can also be made small. On the other hand, if the flat plate comes into close contact with the exposed material without leaving a gap, the following problem will occur. That is, the projection exposure apparatus of the present invention transports the metal film 1 with the drive sprocket biting into the hole 4, but in order to ensure exposure accuracy, it is necessary to make sure that the sprocket and the hole 4 are accurately bitten without any gaps. I have to let it happen. However, if this accurate biting is inhibited for some reason, distortions, wrinkles, etc. will occur in the metal film 1. In this case, if the flat plate is brought into close contact with the metal film, the distortions and wrinkles will increase and cause a shift in the imaging position. In the present invention, since the flat plates 8 and 9 are provided with a slight gap between them relative to the metal film 1, this gap absorbs the distortion and wrinkles of the metal film described above, and the exposure accuracy at the imaging position can be greatly improved. . For example, exposure range
An imaging member measuring 40 mm x 40 mm with a gap of 170 microns between glass plates was attached to a projection exposure device with a focal length of 100 mm, and a test pattern was continuously exposed to a 70 μ thick copper tape coated with photoresist on both sides. As a result of performing etching and measuring the image formation position deviation, it was confirmed that the deviation between the front and back images was 10μ at maximum, and within 5μ on average. In addition, the deviation in the case not according to the present invention was 40 μ at the maximum and 20 μ on average. The above explanation has mainly been given for the case of double-sided exposure, but it also works effectively even for single-sided exposure.
That is, in the case of single-sided exposure, there is no deviation in the imaging position between the front and back sides, but if the pattern is exposed and etched out of alignment with the designed pattern, problems may occur. However, according to the present invention, such inconveniences can also be overcome. In this case, at least the flat plate on the exposure side of the imaging section may be made transparent. In addition, since the other flat plate is simply used as a baking table, it is transparent and
It may be opaque or non-transparent. As described in detail above, according to the present invention, the positional deviation of the image formation is greatly improved, and as a result, the obstacles in etching pattern design are eliminated, and an arbitrary pattern can be photo-etched with high accuracy.

[Brief explanation of drawings]

Fig. 1 is a conceptual configuration diagram showing a conventional projection exposure apparatus, Fig. 2 is a plan view of its imaging section, Fig. 3 is a sectional view thereof, and Fig. 4 shows the imaging state in Fig. 3. Explanatory diagram, Figure 5 is an enlarged view of the main part of Figure 4,
FIG. 6 is an explanatory diagram showing an example of the image formation position deviation state in FIG. 8 are cross-sectional views showing an example of the imaging section in the projection exposure apparatus of the present invention. 1... Material to be exposed (film), 5... Pin for gap adjustment and exposure positioning, 6, 7... Printing frame, 8, 9
...Translucent flat plate.

Claims (1)

[Claims] 1. An exposed material having holes for driving the film formed at regular intervals on both edges of a strip-shaped film is held between printing frames using pins from both sides of the film for positioning the holes, and the exposed surface is In an exposure device that is provided perpendicular to the optical axis and serves as an imaging section,
A flat plate larger than the exposed surface is attached to both printing frames, and at least the exposed side thereof is made translucent, so that when the material to be exposed is held via a pin, there is a gap slightly larger than the thickness of the film between these flat plates. projection exposure equipment.