Method of forming reflective means in a light activated semiconductor controlled rectifier

• US 3,920,495 A
• Filed: 08/29/1973
• Issued: 11/18/1975
• Est. Priority Date: 04/28/1972
• Status: Expired due to Term

• Current Assignee: John S. Roberts
• Original Assignee: John S. Roberts
• Inventors: Roberts, John S.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US05/392,698
• Time in Patent Office: 811 Days
• Field of Search: 156/3,7,8,13,15,17 252/79.3 29/580,583 96/36 317/234,235 65/31 357/19
• US Class Current: 438/705
• CPC Class Codes: G02B 6/2817 using reflective elements to split or combine optical signals
• CPC Class Codes: G02B 6/4202 for coupling an active element with fibres without intermediate optical elements, e.g. fibres with plane ends, fibres with shaped ends, bundles
• CPC Class Codes: G02B 6/4295 coupling with semiconductor devices activated by light through the light guide, e.g. thyristors, phototransistors
• CPC Class Codes: H01L 31/1113 the device being a photothyristor

Abstract

This disclosure is concerned with a method of forming light reflective etch pits preferably having a tetrahedral pattern, in a surface, preferably a (111) surface, of a body of semiconductor material. The body of semiconductor material, preferably silicon, has two opposed major surfaces which are substantially parallel, the body is divided into four alternate regions of opposite type conductivity, the two end regions being emitter regions and the two middle regions being base regions when the body is employed as a light activated four region switch. Activating light enters at one major surface of the body, passes entirely through the body to the opposed major surface where light reflective etch pits cause the light to pass back through the body.

Claims

1. A PROCESS FOR FORMING LIGHT RADIATION REFLECTING TETRAHEDRAL ETCH PITS IN A PRESELECTED SURFACE PORTION OF A BODY OF SILICON COMPRISING MASKING PRESELECTED SURFACE PORTIONS OF A BODY OF SILICON WITH A MATERIAL CAPABLE OF WITHSTANDING HYDROFLUORIC ACID, IMMERSING SAID BODY OF SILICON IN HYDROFLUORIC ACID TO REMOVE ANY OXIDES FROM THE UNMASKED SURFACE PORTION OF THE BODY, IMMERSING SAID BODY IN AN ETCHING SOLUTION FOR A PRESELECTED PERIOD OF TIME WHILE AGITATING THE SOLUTION RELATIVE TOSAID BODY, WHEREBY TETRAHEDRAL ETCH PITS AE FORMED IN THE UNMASKED SURFACE PORTION OF THE BODY SAID ETCHING SOLUTION HAVING BEEN PREPARED BY FORMING A FIRST SOLUTION BY ADMIXING 100 GRAMS OF CHROMIUM TRIOXIDE IN 100 MILLILITERS OF WATER AND JUST PRIOR TO ETCHING ADDING 100 MILLILITERS OF 49% HYDROFLUORIC ACID TO 100 MILLILITERS OF SAID FIRST SOLUTION, AND REMOV ING SAID BODY FROM SAID ETCHING SOLUTION QUENCHING SAID BODY WITH DEIONIZED WATER AND THEREAFTER REMOVING SAID MASKING MATERIAL FROM SAID BODY.

2. The process of claim 1 in which the preselected time ranges from 5 to 10 minutes.

3. The process of claim 1 in which the preselected time is 7 minutes.