US Patent 4,833,790: Scope, Claims, Expiration, and Semiconductor Wafer-Positioning Patent Landscape

US Patent 4,833,790 is not a drug patent. It covers an automated system and method for centering, aligning, and rotationally positioning circular semiconductor workpieces, including silicon wafers. The core invention measures the distance from a fixed rotation center to the wafer edge at multiple rotational positions, calculates the wafer’s lateral offset and angular deviation, and corrects the position through rotation and translation.

The patent issued on May 23, 1989. Under the pre-1995 U.S. patent-term regime, its enforceable term would have expired approximately 17 years after issuance, on May 23, 2006, absent an unusual terminal-disclaimer or other exceptional prosecution history. The patent therefore has no current U.S. exclusionary value.

What technology does US Patent 4,833,790 protect?

The patent protects wafer-handling equipment that performs three related functions:

Transports a circular workpiece along a linear path.
Rotates the workpiece around a fixed spindle or rotation center.
Measures edge distance at multiple angular positions to calculate the offset between the physical wafer center and the machine’s rotation center.

The system then aligns the wafer by applying:

An angular correction, identified in the claims as alpha; and
A translational correction, identified as l.

The claims are directed primarily to semiconductor-wafer handling, although the claim language uses the broader term “circular workpiece.” Potentially covered workpieces could include disks, substrates, optical components, magnetic media, or other circular parts if the claimed structure and operating sequence were present.

The central technical concept is geometric centering. If a wafer is mounted off-center on a spindle, the measured radius from the spindle center to the wafer edge varies as the wafer rotates. At least three measurements allow the control system to determine the magnitude and direction of the offset.

What are the independent claims in US 4,833,790?

The patent has five principal independent claim groups: claims 1, 3, 7, 13, and 17.

Claim	Claim type	Principal subject matter	Key limitations
1	System	Conveying and measuring system	Linear conveyor, rotation about a center on the path, edge-distance measurement, offset calculation at three or more angles
3	System	Cassette-to-spindle handling system	Vertical wafer cassette, elevating mechanism, reciprocating arm, vacuum attachment, spindle, measurement and calculation
7	System	Spindle-based positioning system	Elevating and rotating spindle, detachable workpiece attachment, edge measurement, offset calculation
13	System	Sensor-based centering system	Position sensor reciprocated along the path, measurement of center-to-edge distance, calculation of angular and linear offset
17	Method	Centering and alignment method	Incremental rotation, at least three measurements, calculation of angular and linear offset, corrective rotation and translation

Claims 2, 4-6, 8-12, and 14-16 depend on the system claims. Claims 18-21 depend on the method claim or its algorithmic limitations.

How broad is claim 1?

Claim 1 is the broadest functional system claim in the set. It requires:

A mechanism that conveys the circular workpiece along a linear path;
A mechanism that rotates the workpiece about a center located on that path;
A measuring mechanism that determines the distance from the rotation center to the workpiece periphery; and
A determining mechanism that calculates offset from measurements taken at at least three angular positions.

The claim does not require:

A semiconductor wafer;
A cassette;
A vacuum chuck;
An optical sensor;
A particular motor;
A specific computer architecture;
A specific mathematical equation; or
A particular wafer diameter.

That breadth is narrowed by the required combination. A system that merely detects the wafer edge, rotates a wafer, or centers a wafer through a vision system would not necessarily meet claim 1. The accused system must use the claimed relationship between a fixed rotation center, multiple angular measurements, and calculated offset.

Claim 1 is likely vulnerable to design-arounds that use:

A camera or machine-vision system to locate the wafer center directly;
Multiple fixed sensors rather than a measurement along the linear path;
A chuck that moves the wafer without measuring radial distance from the rotation center;
A non-linear conveying arrangement;
A centering algorithm based on edge imaging rather than distance measurements at multiple rotation angles.

What additional structure does claim 3 require?

Claim 3 narrows the invention to a wafer-handling architecture involving:

A cassette containing multiple horizontal workpieces in a vertical stack;
A cassette elevator;
A reciprocating arm;
An arm end that enters the cassette;
A detachable workpiece attachment mechanism;
A spindle positioned away from the cassette but near the arm’s linear path;
Rotation about a center on the linear path;
Edge-distance measurement; and
Offset determination using at least three angular measurements.

Dependent claims add specific mechanical details:

Claim 4 requires at least one guide rod parallel to the path and a translating arm.
Claim 5 specifies a vacuum port at the remote end of the arm.
Claim 6 specifies a J-shaped arm end that circumscribes the spindle at a selected position.

These limitations describe a practical semiconductor wafer-transfer machine rather than a generalized centering algorithm. An accused system would need to satisfy the cassette, arm, spindle, and transfer-path limitations for literal infringement of claim 3.

The J-shaped arm limitation in claim 6 is particularly narrow. A straight blade, end effector, or robotic arm with a different geometry may avoid literal infringement, although the doctrine of equivalents could become relevant in a live dispute.

What does claim 7 cover?

Claim 7 focuses on a spindle-based positioning arrangement. It requires:

A conveyor;
A spindle near the conveyor path;
A detachable workpiece attachment structure on the spindle;
Selective elevation and rotation of the spindle;
Measurement of the distance from the rotation center to the workpiece edge; and
Calculation of offset from at least three rotational measurements.

Claims 8-12 narrow the claim as follows:

Dependent claim	Limitation
8	Rotation center located on the linear path
9	Distance measured along the linear path
10	Detachable attachment includes a vacuum port
11	Spindle is a cylindrical shaft with a vacuum port at one end
12	Elevation and rotation include a controllable motor

Claim 7 is structurally broader than claim 3 because it does not require a cassette, reciprocating transfer arm, or J-shaped arm. It is narrower than claim 1 in other respects because it expressly requires a spindle with selective elevation and rotation.

What does claim 13 add through the position sensor?

Claim 13 requires a conveyor, a raising and rotating mechanism, and a position sensor that reciprocates along at least part of the linear path. The sensor measures the distance between the rotation center and the wafer periphery.

Claims 14-16 specify:

An optical sensor;
A drive screw and carriage for moving the sensor; and
A controllable motor connected to the drive screw.

This claim group is important because it distinguishes the sensing architecture from the spindle and wafer-transfer structures in claims 3 and 7. A system could potentially fall within claim 13 even if it used a different wafer-transfer arrangement, provided it used a reciprocating position sensor to make the required distance measurements.

The use of “means for reciprocating” and “means for determining” may invoke 35 U.S.C. § 112(f), formerly § 112, paragraph 6. If so, the scope may be limited to the corresponding structures disclosed in the specification and their statutory equivalents, rather than every technology capable of performing the stated function.

What method does claim 17 protect?

Claim 17 covers the operating sequence rather than a particular machine architecture. It requires:

Incrementally rotating a circular workpiece about a fixed center that does not coincide with the workpiece center;
Measuring the center-to-periphery distance at at least three different rotation angles;
Calculating angular deviation and linear offset;
Rotating the workpiece through the calculated angular correction; and
Translating the workpiece through the calculated linear correction so the two centers coincide.

This is the patent’s most important algorithmic claim. It may read on equipment made by different manufacturers if the equipment performs the same measurement and correction sequence.

Claim 18 adds a post-centering operation:

Rotating the workpiece to detect discontinuities in its circular periphery; and
Rotationally positioning the workpiece so the discontinuities align in a selected pattern.

This limitation could apply to wafers with flats, notches, orientation marks, or other peripheral discontinuities.

Claim 19 requires repeated measurement to confirm the calculated angular and linear corrections. Claims 20 and 21 add algorithmic limitations for calculating alpha and l from the measured distances. The text supplied for claim 21 does not reproduce the equation, but the claim clearly narrows claim 20 by specifying the mathematical determination of the offset length.

How would infringement of US 4,833,790 be analyzed?

A literal infringement analysis would normally proceed element by element.

Technical issue	Infringement question
Circular workpiece	Does the equipment handle a circular wafer or equivalent disk?
Fixed rotation center	Does the workpiece rotate around a defined center?
Linear path	Does the relevant conveyor, arm, or sensor move along a linear path?
Edge-distance measurement	Is distance from the rotation center to the workpiece periphery measured?
Multiple angles	Are measurements taken at three or more angular positions?
Offset calculation	Does software or control logic calculate center displacement?
Correction	Does the system rotate and translate the workpiece to align centers?
Structural details	Are the claimed cassette, spindle, vacuum port, sensor, carriage, or motor present?

The strongest infringement risk would arise from a wafer aligner that rotates a wafer on a spindle, measures edge position at multiple angles with a linear optical sensor, calculates eccentricity, and translates the wafer to center it.

The weakest risk would arise from a modern vision-based aligner that captures a two-dimensional wafer image and calculates the wafer center without measuring radial distance from a fixed rotation center at multiple angular positions.

When did US Patent 4,833,790 expire?

US Patent 4,833,790 issued May 23, 1989. Patents based on applications filed before June 8, 1995 generally received a term of 17 years from grant under the pre-Uruguay Round Agreements Act framework. The resulting expiration date is approximately May 23, 2006.[1][2]

Event	Date
Patent issued	May 23, 1989
Approximate statutory expiration	May 23, 2006
Current enforceability	Expired
Current U.S. blocking right	None

The patent cannot support a present-day U.S. infringement action unless an unusual legal record altered the ordinary term calculation. Patent expiration eliminates the exclusionary right, although the patent remains relevant as prior art and as evidence of historical technology.

What is the Orange Book status of US Patent 4,833,790?

There is no Orange Book status. The patent does not claim a pharmaceutical active ingredient, formulation, dosage form, method of treatment, or drug-delivery system. It is directed to industrial automation and semiconductor wafer positioning.

The patent therefore has:

No FDA regulatory exclusivity;
No New Drug Application association;
No Orange Book listing;
No Paragraph IV certification relevance;
No generic-drug entry date;
No biosimilar relevance;
No pharmaceutical formulation protection.

FDA approval, Hatch-Waxman litigation, biosimilar competition, and drug patent-term extension concepts do not apply to this patent.[3]

What companies and technologies compete in this patent landscape?

The relevant commercial landscape is semiconductor wafer handling and alignment equipment. Major technology categories include:

Wafer aligners and pre-aligners

These systems center and orient wafers before processing. They may use:

Edge-contact rollers;
Optical edge sensors;
Laser displacement sensors;
Camera-based machine vision;
Vacuum chucks;
Notch and flat detection;
Rotary spindles with vertical lift.

Semiconductor equipment suppliers

Companies active in adjacent wafer-handling and automation markets have included Applied Materials, Tokyo Electron, KLA, Brooks Automation, Genmark Automation, Rorze, and Asyst Technologies. Their current products and patent portfolios must be assessed by product generation and jurisdiction. Company participation in the market does not establish infringement of US 4,833,790.

Modern design-around approaches

Later systems commonly reduce exposure to this patent’s claim language by using:

Full-field imaging rather than one-dimensional edge-distance measurements;
Fixed-camera triangulation;
Multiple sensors mounted around the wafer;
Robotic end-effectors with integrated alignment;
Software centering from notch or flat geometry;
Direct coordinate transformation from image data.

The patent’s expired status means the commercial question is no longer freedom to operate under this specific patent. The relevant issue is whether later patents cover the particular sensor, robot, chuck, inspection, or alignment implementation.

How strong was the patent estate?

The patent appears to have had meaningful historical coverage because it used several independent claim formats:

Broad system architecture in claim 1;
Cassette and transfer-arm architecture in claim 3;
Spindle architecture in claim 7;
Reciprocating-sensor architecture in claim 13;
Algorithmic method coverage in claim 17.

That diversification reduced dependence on a single machine configuration. The claims also covered both hardware and operating steps, which could have complicated design-around efforts during the patent term.

Its limitations were equally important:

The claims require a circular workpiece;
Several claims require a linear path;
The measurement must involve distance from the rotation center to the periphery;
At least three angular measurements are required;
Some claims require specific spindle, cassette, vacuum, or sensor structures;
The method claims require calculated angular and translational correction.

The estate is now legally weak for commercial purposes because it is expired. It retains technical and prior-art value, but no current U.S. licensing leverage or litigation leverage.

What licensing and litigation risks exist today?

No current licensing obligation or active litigation right arises solely from US Patent 4,833,790 because the patent expired in 2006. Any historical license, settlement, covenant not to sue, or assignment could remain relevant to contract interpretation, but the patent itself cannot impose a continuing patent royalty obligation after expiration without a separate enforceable contractual basis.

No current Paragraph IV challenge, generic launch dispute, biosimilar dispute, or FDA patent-listing dispute is associated with this patent.

The practical litigation risk has shifted to:

Later patents claiming optical alignment systems;
Patents covering wafer-notch detection;
Robotic wafer-transfer mechanisms;
Vacuum end-effectors;
High-speed rotary chucks;
Machine-vision centering algorithms;
Integrated semiconductor-tool control systems.

What geographic coverage does the patent have?

US Patent 4,833,790 provides rights only in the United States. A U.S. patent does not automatically cover:

Equipment manufactured abroad;
Equipment sold abroad;
Foreign semiconductor fabs;
Foreign subsidiaries;
Exported systems, unless U.S. law is otherwise implicated.

Foreign counterparts would require a separate family review. The supplied claim set establishes the U.S. claim scope but does not establish corresponding rights in Europe, Japan, Taiwan, South Korea, or other jurisdictions.

Key Takeaways

US Patent 4,833,790 is a semiconductor wafer-centering and alignment patent, not a drug patent.
Its core invention measures wafer-edge distance from a fixed rotation center at three or more angles.
Claims 1, 7, 13, and 17 provide the principal broad coverage.
Claims 3 and 6 narrow protection to cassette, arm, spindle, and J-shaped transfer structures.
Claims 18-21 address notch or peripheral-feature alignment and mathematical offset calculations.
The patent issued on May 23, 1989 and approximately expired on May 23, 2006.
It has no current Orange Book, Hatch-Waxman, Paragraph IV, biosimilar, or FDA exclusivity relevance.
Its historical strength came from covering multiple machine architectures and the centering method itself.
Current freedom-to-operate analysis should focus on later patents covering wafer aligners, machine vision, optical sensing, robotics, chucks, and semiconductor automation.

FAQs

Is US Patent 4,833,790 a semiconductor wafer patent?

Yes. Although the claims say “circular workpiece,” the cassette, wafer-transfer arm, spindle, vacuum port, and rotational alignment features identify semiconductor wafer-handling equipment as the principal application.

Can an expired patent still block a wafer-aligner product?

No. An expired patent cannot support an infringement claim based on conduct occurring after expiration. It can remain relevant as prior art against later patent applications.

Does a camera-based wafer aligner infringe claim 17?

Not necessarily. Claim 17 requires measuring the distance between the rotation center and the workpiece periphery at at least three angular positions. A camera system that directly calculates wafer-center coordinates may avoid that limitation, subject to the actual implementation and equivalents analysis.

Does the patent cover wafer-notch detection?

Claim 18 covers rotational positioning after centering to align discontinuities in the circular periphery. This can include a wafer notch or flat if the claimed centering and subsequent alignment sequence is performed.

Is there a current royalty obligation under US Patent 4,833,790?

Not from the patent alone. Any continuing obligation would have to arise from a separate contract, license, settlement, or other enforceable agreement.

References

United States Patent and Trademark Office. (n.d.). Patent term calculator and patent term guidance. U.S. Department of Commerce.
United States Patent and Trademark Office. (1989). United States Patent No. 4,833,790.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.

Details for Patent: 4,833,790

Summary for Patent: 4,833,790