Annotation Examples

This page contains a number of examples that show how the annotation directives operate. We will use a small and simple panel with 6 circuits.

Figure 1 - the test panel for our annotation examples: test_panel.gds.

Layer 1 - metal layer (black)

Layer 2 - reserved areas for text annotation (green)

Layer 3 - text coordinates for insertion (blue)

Layer 63 - construction lines (cyan)

SFGEN SETTINGS

For each example, we always use the same SFGEN settings. We process layer 1 for output (the other layers were created primarily to help us compute the insertion points for the annotation text).

Figure 3 - SFGEN Main Dialog showing test_panel.gds loaded and layer 1 selected.

The Annotation Insertion File

The insertion file has two main sections: a GLOBAL (mandatory) section followed by one or more TEXT_ANNOTATION sections. For our examples, we will mostly keep the GLOBAL directives constant (unless specifically noted where we are exercising some of the global directives) and it is show below:

GLOBAL Section

Example 1 - A Simple Text Insertion

We are going to insert a text annotation in the lower left circuit. Based on our layout, the text will be left (bottom) justified, it will be inserted at coordinates 2350,500 and we will set it to 1250 um high. The string is 800-555-2000-004 and we will use the font called bcssemi.ttf.

Here is the text annotation section which follows the global section:

B_TEXT_ANNOTATION
HEIGHT 1250
FONT bcssemi.ttf
XY 2350 500
B_STRING
800-555-2000-004
E_STRING
E_TEXT_ANNOTATION


Figure 5 - Results of example 1 - annotation placed in lower left circuit

Notes:

1. The annotation polygons were placed on layer 0 - not layer 1. (this is default behavior)

2. The annotation polygons were generated into a cell and the cell was inserted. (due to the OUTPUT_CLASS=hierarchy)

---

Example 2 - Use of the Inverse Directive

If you need to place a text annotation where there is already digitized data, you can use the inverse directive to "cut" away the text. Let's see how that works. We are going to place a string, "800-555-2000" at coordinate 55500,-2500 with height = 2000 at the lower right of the panel. There is already digitized data there.

Figure 6 - Left: text height = 2000. Right: text height = 1600 and MARGIN = 200.

Notes:

1. I ran this twice - first with the text height=2000 but it looked ugly (left)

2. The second run (right) I reduced the text height to 1600 and added a 200 um margin. This looks better.

3. While our viewer seems to imply that the metal on Layer 1 was removed to generate the annotation, it was not. Instead, polygons were generated on layer 0 that must be "scratched" away by the rasterizer. This is a bit of a cheat but since our target is rasterization (and the rasterizer can easily do the scratch) this is an efficient approach. However there is a big limitation to this approach: if you have multiple text annotations, you cannot have both positive and inverse annotations at the same time!

Example 3 - Text Justification, Mirroring and Rotation

Let's look at some examples where we combine a MIDDLE-MIDDLE justification with rotation and miroring. First, we are going to demonstrate the effect of changing the vertical justification:

Figure 8 - Text annotation position for VJUST = BOTTOM, MIDDLE, TOP

Now we are going to return the VJUST back to MIDDLE for all three circuits and apply rotation of 90, 180 and 270.

Figure 9 - Since the insertion point is at the center of the text bounding box, the rotation also proceeds around that point.

Let's see how mirroring along X and Y work with the MIDDLE-MIDDLE text insertion.

Figure 10 - Since the insertion point is at the center of the text bounding box, one does not have to compute the mirror anchor points to keep the location from "flying" away.

Examples Page 2 ...