# US 10,319,612 B2 · Method for the rapid processing of polymer layers in support of imidization processes and fan out wafer level packaging including effiecient drying of precursor layers

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- Number: US 10,319,612 B2
- Document ID: US10319612B2
- Status: Granted
- Kind: B2
- Application number: 16/174,260
- Filed: 2018-10-29
- Published: 2019-04-11
- Granted: 2019-06-11
- Earliest claimed: 2016-01-21
- Assignees: Yield Engineering Systems, Inc.
- Applicants: Yield Engineering Systems, Inc.
- Inventors: William Moffat
- Web page: https://patentgrep.com/patent/US10319612B2

## CPC

- H10P 72/0408: {for drying}
- B32B 27/281: {comprising polyimides}
- B32B 2250/24: All layers being polymeric
- B32B 2274/00: Thermoplastic elastomer material
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM

## Abstract

A process for the drying, and subsequent imidization, of polyimide precursors which minimizes or eliminates voids and which minimizes or eliminates discoloration. The process uses a sequential set of descending pressure operations that allow for time efficient processing of wafers. The set of descending pressure operations are interspersed with evacuation processes using heated gasses, which combine heating and byproduct evacuation. The process results in layers with reduced or eliminated voiding, discoloration, and solvent retention.

## Claims

### Claim 1

A process for drying of substrates in support of temperature imidization of polymer layers, said process comprising the steps of:
inserting one or more substrates into a process chamber, said one or more substrates coated with a layer of polyimide precursor, said polyimide precursor comprising N-Methyl-2-pyrrolidone;
reducing the pressure in said process chamber to a first drying pressure;
first flushing said process chamber with inert gas to a first flushing pressure;
reducing the pressure in said process chamber to a second drying pressure after said first flushing, wherein said second drying pressure is lower than said first drying pressure;
second flushing said process chamber with inert gas to a second flushing pressure after the step of reducing the pressure in said process chamber to a second drying pressure;
reducing the pressure in said process chamber to a third drying pressure after the step of second flushing said process chamber, wherein said third drying pressure is lower than said second drying pressure; and
third flushing said process chamber with inert gas to a third flushing pressure after the step of reducing the pressure in said process chamber to a third drying pressure.

### Claim 2 (depends on 1)

The process of claim 1 wherein said process chamber is heated to a first chamber temperature.

### Claim 3 (depends on 2)

The process of claim 2 wherein said first flushing said process chamber with inert gas comprises flushing with inert gas heated to a first gas temperature.

### Claim 4 (depends on 3)

The process of claim 3 wherein said second flushing said process chamber with inert gas comprises flushing with inert gas heated to a second gas temperature.

### Claim 5 (depends on 4)

The process of claim 4 wherein said third flushing said process chamber with inert gas comprises flushing with inert gas heated to a third gas temperature.

### Claim 6 (depends on 5)

The process of claim 5 wherein said first chamber temperature is in the range of 135 C to 180 C.

### Claim 7 (depends on 6)

The process of claim 6 wherein said first drying pressure is in the range of 30-60 Torr.

### Claim 8 (depends on 6)

The process of claim 6 wherein said first drying pressure is in the range of 30-50 Torr.

### Claim 9 (depends on 8)

The process of claim 8 wherein said second drying pressure is in the range of 15-30 Torr.

### Claim 10 (depends on 9)

The process of claim 9 wherein said third drying pressure is in the range of 1-15 Torr.

### Claim 11 (depends on 1)

The process of claim 1 wherein said first gas temperature is in the range of 135 C-180 C.

### Claim 12 (depends on 11)

The process of claim 11 wherein said first gas temperature is in the range of 135 C-180 C.

### Claim 13 (depends on 11)

The process of claim 11 wherein said second gas temperature is in the range of 135 C-180 C.

### Claim 14 (depends on 12)

The process of claim 12 wherein said second gas temperature is in the range of 135 C-180 C.

### Claim 15 (depends on 13)

The process of claim 13 wherein said second gas temperature is in the range of 135 C-180 C.

### Claim 16 (depends on 14)

The process of claim 14 wherein said second gas temperature is in the range of 135 C-180 C.

### Claim 17 (depends on 16)

The process of claim 16 further comprising the step of temperature imidizing a polymer layer on said one or more substrates after the step of third flushing said process chamber while having maintained the low oxygen level of the drying steps.