# BOE chemical waste disposal SOP (UWaterloo)

## Purpose

To ensure the safe collection, storage, and disposal of buffered oxide etch (BOE) waste generated during silicon dioxide wet etching processes.

This SOP minimises risks associated with toxic fluoride exposure, corrosive chemical handling, and environmental contamination.

## Scope

This procedure applies to:

* HF solutions used for oxide etching
* Buffered oxide etch (NH₄F + HF)
* HF-contaminated rinse water
* Any fluoride-containing liquid waste generated during the etching process

## Responsibilities

**Operator**

* Follow waste collection procedures
* Label waste containers correctly
* Report spills immediately

**Process Lead / Lab Supervisor**

* Ensure proper containers and labels are available
* Verify waste storage compliance

## Required Equipment and Materials

* HF-compatible waste container (HDPE or polypropylene)
* Secondary containment tray (it catches chemicals if the primary container has leaks/spills)
* Hazardous waste labels
* PTFE or plastic funnels
* HF spill kit
* Calcium gluconate gel (for emergency exposure)
* HF safe gloves; safety glasses

## Waste Collection Procedure

### Step 1 – Preparation

* Ensure the waste container is made of HF-compatible plastic (never glass; HF dissolves glass).
* Verify the container is placed in secondary containment.

### Step 2 – Waste Transfer

* After etching, transfer the used HF/BOE solution into the designated HF waste container using a plastic funnel.
* Do not overfill containers 

### Step 3 – Rinse Waste

* Collect any HF-contaminated rinse water in the same labelled waste container unless instructed otherwise by lab policy.

### Step 4 – Labelling

* Chemical contents: HF / BOE with fluoride ions
* Hazard class: Corrosive, toxic
* Date
* Lab location
* Responsible researcher

## Storage Requirements

HF waste containers must:

* Be stored in secondary containment
* Remain closed when not in use
* Be kept in the designated chemical waste storage area
* Never be stored in glass containers

## Waste Disposal

When the container approaches 80% capacity:

1. Seal the container.
2. Submit a hazardous waste pickup request through the institutional chemical waste disposal system (e.g., Waterloo ESF).
3. Store waste in the designated waste accumulation area until pickup.

## Emergency Procedures

### Chemical Spill

* Evacuate area if necessary.
* Use HF spill kit to neutralize and contain the spill.
* Report incident to lab supervisor and safety office.

### Skin Exposure

* Immediately rinse affected area with running water for at least 15 minutes.
* Apply calcium gluconate gel to exposed area.
* Seek medical attention immediately.

## PPE Requirements

Personnel must wear:

* Lab coat
* Chemical-resistant gloves (HF-rated)
* Safety goggles
* Headgear + Face shield
* Neoprene apron


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