Diamond Scribing Tools

* T - Bar Scribes now available
along with Refurbishing Service

 

Semicon Tools, Inc. has been manufacturer of scribing tools for wafer dicing and diamond precision cutting wheels for over 30 years. STI acquired the assets, patents and technology in July of 1983. Originally a division of American Coldset Corporations dating back to 1963.

V4-46 or V4-64
has four lapped vees for heel scribing and four lapped cutting edges for toe scribing.
V4-P-46 or V4-P-64
has four lapped vees for heel scribing only.
904-90
has four lapped cutting edges for toe scribing only.
912-90 or 912-60
has two cutting edges for toe scribing between protrusions on wafers.

904-90- A truncated scriber with four lapped cutting edges for toe scribing only.

912-90- A bi-scribing tool developed by STI, has two cutting edges for toe scribing between protrusions on wafers. Although the shank of the 912 has four flats, only two of these flats correspond to the cutting edges. These flats are color coded.

912-60- Same as the 912-90 but here the roof angle has been reduced from 90 degrees to 60 degrees to permit scribing between even more closely spaced protrusions.

V4-P-46 or V4-P-64 - A highly sophisticated scribing tool developed by STI for heel scribing only. The V-4 has four lapped vees for heel scribing available with an included angle of 46 degrees -64 degrees. The customary table is no longer present with the primary facets coming to an approximate point.

V4-46 or V4-64 - A highly sophisticated truncated scribing tool developed by STI. The V4 has four lapped vees for heel scribing and four lapped cutting edges for toe scribing. The V4 is available with an included angle on the shaped vee of 46 degrees -64 degrees.

SEMICON TOOLS offers a reconstruction service for worn out scribing tools

NOTE: Scribing tools have 1 and one fourth inch shank lengths SEMICON TOOLS offers a reconstruction service for worn out scribing tools.

SCRIBING TOOL SET UP PROCEDURE

The following procedure is to be considered in general terms and is applicable in intent for any and all scribing machines.

1. Turn depth control of the scribing machine arm to its zero setting. The depth control is the device that determines the stopping point of the scribing arm maximum down position.

2. Cycle the scribing machine into its prescribed set up position with a test wafer (scrap wafer of equivalent thickness) for trial scribing on the chuck.

3. Insert the scribing tool into the tool holder with the appropriate edge in the direction of scribing travel. Tighten the clamp gently to just support the tool. Adjust the angular relationship relative to the wafer surface. Make reference to the tabulated angular tables on the reverse side of the drawing corresponding to the specific tool in use.These tables represent the geometric configuration of the tool with relationship to its angular projection with the wafer surface for a given scribe trench dimension. Experimentation by the user will be necessary to determine what angular relationship best suits his scribing needs for a specific material. In general, best scribing results are obtained when the cutting edge approximates parallel with the surface of the wafer. Slight variations in the angular relationship change the scribing method from toe scribing to heel scribing or vice versa.

4. Adjust the scribing tool axially in the holder (be careful not to change the angle) so that the cutting edge of the scriber just touches the wafer surface ( or take a piece of paper the same thickness as the wafer moving it around so it is easy to determine when the tool touches). Now firmly clamp the tool into the tool holder assuring no further angle or axial change. NOTE: Polishing of the diamond scriber is performed with reference to the flat on the shank with all facets and intersecting planes forming edges with relationship thereto. All other dimensions such as over-all length, shoulders on the shank between the diameter and the flats, the length of the flats, or other axial relationships cannot be used as any reference in set-up procedure.

5. Adjust the depth control to the desired depth of scribe depending upon the material, the thickness of the wafer, and the surface conditions prevailing.

6. Adjust the applied pressure to the scribing tool edge to achieve the depth of scribe desired.

7. Using a scrap of wafer make trial scribe lines in both the "x" and "y" direction. Break and examine the edges for clean, unsplintered 90 degree intersects.

8. Readjust tool angle and pressure as required.

Traversing Speed

Traversing speed is referred to as the rate which the scribing tool is traversing across the surface of the wafer. Assuming the surface of the material being scribed is uniform in quality and flatness, rate of traverse should not be predominant factor in achieving a quality scribe and a satisfactory break. It is important, however, to consider the physical relationship of the tool prior to wafering engagement. tools suspended excessively below the surface of the wafer tend to bounce when hitting the edge of the wafer upon entry on the street.

Tool Pressure

In order to achieve scribing, adequate force must be applied to overcome the surface tension of the material under the edge of the scribing tool. This is a variable function depending upon the material, geometric shape of the edge of the tool, and the degree of stress to be imparted into the wafer. The scribing machine manufacturer designs into the mechanism a means for controlling and varying the amount of force to be applied and, for the most part, generally force in the 15 gram range will be adequate providing all other mechanisms are in balance. The applied force is extremely critical and the most important single variable in producing the desired scribe. Unfortunately the pressure indicator on many machines on the market are not sensitive enough and not repetitive between machines for a specific setting. Each machine should be calibrated with an external measuring device for both actual weight and range of change.

Wafer Breaking

Wafer breaking is the process of utilizing the scribes to force crack propagation at the predetermined points. In as much, as the mechanics of breaking is one of interrupted surface tension at high stress locations, any change in these applied properties would reduce their effect. Many materials, including those used in the wafers tend to self anneal reducing the applied stress. It is, therefore, of great benefit to utilize the scribe line as soon after it has been applied as physically possible.

NOTE: Semi-conductor material is a crystalline product which has orientation and cleavage plans. Breaking or crack propagation tend to follow the particular crystalline structure. It is essential that the crystal itself be oriented accurately and the photomasking which determines the direction of the scribe be accurately related to the crystal structure. Orientation of both the crystal and photomasking to be compatible within three degrees of the natural cleavage planes.

Tool Quality

STI prides itself on the quality and uniformity of the scribing tools it manufactures. Present configuration, quality of workmanship, consistency from tool to tool are in accordance with the individual drawing illustration. Each tool is manufactured with as near perfect octahedron shaped diamond crystal as is readily obtainable and free from any cracks, impurities, or discontinuities occuring in the toe, heel, and cutting edge.

Inspection

STI inspects all tools by the following method and recommends this for quality control:

a.
    Use of a stereomicroscope rather than a metallurgical microscope.
b.    Diamond must be transparent to permit inspection of interior quality. Color of diamond is critical.
c.    Tool must be made from a crystal octahedron shape. Color should be white or yellow.
d.    All cutting edges must coincide with the hardest planes of the diamond. Verify via X-Ray.
e.    At low magnification (50x) no inclusions or discolored spots shall be visible within 0.002 inches of a cutting edge.
f.     No tools showing evidence of internal fractures are acceptable.
g.    On toe scribing tools the diamond must be free of chips along 0.005 inches of the top edges starting from each corner. Inspect at 100 x. Verify at 400 x.
h.    For heel scribing tools no chips must be visible along 0.005" of the edges and 0.005" of the cutting edge nearest to the V of the heel and0.002" of the edges of the V itself. Inspect at 100x. Verify at 400x.
i.     The table may be rectangular as long as the corners are 90 degrees as each cutting edge is set up individually.
j.     For heel scribing the cutting edge must bi-sect the V within the print tolerance and the plane of the V must be in relationship to the locating flat on the shank within print tolerance.                
k.   When using unlapped heels special care must be taken to verify that conditions stated in Paragraph j are met.
l.    The diamond should be swabbed with acetone to facilitate inspection.
m.  Do not inspect diamond using a shadowgraph for internal flaws, only for surface measurement.

In this specific instance scribing tools are composite in nature, manufactured from a steel shank, that has a tungsten/carbide brace of a diamond to one end. The scribing function is built around and related to the physical properties of diamonds and, therefore, a brief review of pertinent diamond properties would seem appropriate at this time.

Hardness is the main property which comes to mind when diamonds are mentioned. On Mohs hardness scale diamond is rated at 10. (On the Mohs scale it will be rated at 15.)

Material -- Pure Carbon (C)

Streak -- Colorless

Cleavage -- Octaherdral

Luster -- Adamatine

Density -- 3.40 - 3.52 GM/CC

Color -- Colorless or Pale Yellow, may be Red, Orange, Green, Blue, Black. Transparency -- Transparent, Opaquein Polarized Light.

Form -- Octahedral Crystals, Flattened, Elongated, with curved faces.

Molecular Structure -- Convalent Bonding.

System Class -- Cubic

Indacatrix -- Isotropic

Melting Point -- 3700 degrees C + 100 degrees

Compressibility -- 0.16 x 10-6 Sq. CM/KG.
                        -Q.18 x 10-6 Sq. CM/KG.

Thermal Conductivity - 0.35 gCal/CM Second Degree

Thermal Resistance - 0.69 CM deg/w

Diamond Density = (Unit Cell Content) (Atomic Weight) (Atomic Mass Unit GM)


(Perfect Crystal) (Unit Cell Volume A) 3 CC
Unit Cell Content = 8
Atomic Weight = 12.0115GM
Atomic Mass Unit = 1.66 x 10 - 24
Unit Cell Volume = 3.567 Angstrom
Angstrom = 10.B CC
= 8(12.0115) (1.66 x 10-24)GM (1.595 x10-22)GM
( 3.567 x 10-8) 3 CC = (4.538 x 10-23)CC
Diamond Density = 3.51476 GM/CC
(Perfect Crystal)

Diamond crystallizes in the cubic system, the simplest forms of which are the octahedron and the cube. the crystal can be cleaved along planes which lie parallel to the triangular face of the octahedron. Perpendicular to these cleavagr planes diamonds offer great resistance to abrasion. The economic manufacturing and use of industrial diamond tools often depend upon the ability to recognize this structure. STI refers to it as orienting and strives to orient each diamond to the advantage of this characteristic. However, diamonds used for scribing tools are naturally formed and attention must be brought to the variable nature of the diamond emphasizing that, not only do different diamonds have appreciably different structure and mechanical properties, but different parts of the same stone may differ appreciably. The scribing tool is lapped into predetermined symmetrical relationships which are designed to coincide with the hard vector or orientation. This, however, cannot always be achieved due to the irregularities of warping, twisting, molecular overlap that sometimes occur within a specific stone. X-ray methods are the only means to accurately determine the grain direction.

The hardness of the diamond depends greatly on the crystallographic relationship and, therefore, each crystal must be set with a view towards exposing the hard plane of the diamond to the work piece. Thus, orientation of the diamond in the industrial tool is of the utmost importance. If the diamond were set at random, softer directions would be exposed to the work piece resulting in greater inconsistency and shorter tool life. Only near perfect crystals are used striving to achieve uniformity of all components. STI has pioneered this concept and all our diamond scribing tools are fully oriented, to the most advantageous condition of each individual diamond.

Scribing
It might be well worthwhile to review some of the most critical areas in utilizing scribing tools in general. Specific conditions vary between processes, material being scribed and procedures for production:

Tool Types
This refers to the manner of attack of the tool to the wafer and is generally referred to as "heel" scribing or "toe" scribing(detailed illustration on back of each individual tool specification sheet.)
Scribing
Scribing for the purpose of breaking is achieved by interrupting the normal surface tension of a specific material creating a high stress, notched zone, at the point of the desired break. This effect can be achieved with a minute scribe. Every effort should be used to maintain continuous contact between the scribe edge and the wafer. As the tool travels over the wafer, a stress pattern will be created in the silicon (or material being scribed).
Discontinuity in the scribing line interrupts the the predetermined path of crack propagation resulting in irregularity, spalling, chipping, and retention of unrelieved stresses.




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