resistanc collectod ean r capacit foune yar o t d commercial silicon controlled rectifier, today's necessarye b relative .Th e advantage lineaf so r thyristor. This later wor alss kowa r baseou n do and circular structures are considered both for 1956 research [19]. base resistanc r collectofo d an er capacity. Parameters, which are expected to affect the In the process of diffusing the p-type substrate frequency behavior considerede ar , , including wafer into an n-p-n configuration for the first emitter depletion layer capacity, collector stage of p-n-p-n construction, particularly in the depletion layer capacit diffusiod yan n transit redistribution "drive-in" e donophasth f ro e time. Finall parametere yth s which mighe b t diffusion at higher temperature in a dry gas obtainabl comparee ear d with those needer dfo ambient (typically > 1100°C in H2), Frosch a few typical switching applications." would seriously damag r waferseou wafee Th . r surface woul e erodedb pittedd an d r eveo , n The Planar Process totally destroyed. Every time this happenee dth s e apparenlosexpressiowa th s y b tn o n The development of oxide masking by Frosch Frosch' smentiono t face t no , ourn o , s (N.H.). and Derick [9,10] on silicon deserves special We would make some adjustments, get more attention inasmuch as they anticipated planar, oxide- silicon wafers ready, and try again. protected device processing. Silicon is the key ingredien oxids MOSFEr it fo d ey an tpave wa Te dth In the early Spring of 1955, Frosch commented integrated electronics [22]. An account of their to Holonyak t again,i ,d "Weldi "e meaninw l g revolutionary developmen utilizatiod an t f SiOno s 2a e waferth s were again destroyed t thee Bu .nh vitae th l foundatio f today'o n s 1C industr s beeyha n smile displayed dan silicoe dth n wafer - snic e described by Holonyak [22]: and gree n coloi n n furthe(i r r instances also s techniciahi d an pink) ne H Deric. d ha k buildinn "I r variougou s experimental devices, switched from a dry-gas (typically N2 or H2) we were in contact with various groups and impurity diffusio wet-ambiena o nt t (H2O vapor individuals, but above all with Carl Frosch. carrie+ r gas) diffusion a consequenc, n a f o e Frosc consummata s hwa e process chemiso twh accident of the exhaust H2 igniting and flashing- was familiar with many types of processing back int diffusioe oth n chamber (becauss ga f eo procedure d beeha n d workingan s , wits hi h flow fluctuations) and causing H2O to cover, technician Derick n impurito , y diffusion into react with protecd an , silicoe th t n samples with silicon for several years. In spite of his oxide. The "wet" ambient, which was then considerable experience, Frosch, with dry gas immediately evaluated and adopted, created a diffusion procedures utilizing N2 or H2, protective oxide on silicon. It could be regularly reduced many of our silicon wafers to selectively remove r gaseoudfo s diffusion into "cinders, " particularly at higher temperatures the bare regions, which could the resealee nb d with oxide for higher temperature anneals or further diffusion. Many processing sequences Because we had mastered building a diff used- protective th coul f o devisee e db eus r oxidedfo , base alloyed-emitter silicon p-n-p transistor (in which f courseo , , prevented crystal pittind gan r problemspitou f o e s with diffusion)f o e on , erosion. Frosch and Derick quickly found out the p-n-p-n configurations that we could which impurities were blocked from diffusion explore was simply a modification of the p-n-p into silicon by the natural protective oxide (SiO ) transistor coule :W d fabricat diffused-base eth e 2 created in an H2O-vapor ambient and which alloyed-emitter p-n-p on one side of a p-type impurities would permeate the oxide (e.g., Ga). substrate wafer after it first was prepared with It was easy, once the issue of the oxide was an n-type diffused region (symmetrical) on known deviso t , e various scheme diffuso st e into both wafere sideth f o s. Either side coule db bloco t r o k impurity diffusion into silicone Th . chosen to form the p-n-p. The result was a p-n- process was so flexible that planar n-type p-n switch, in fact, the p-n-p-n switch of regions of any desired pattern could be prepared s exampla describe ) (b en i [19]d . (The o p-typna e substrate silicon oppositee th r o , - p , complementary versio f thino s exact structure, on-n diffused regions could be prepared on n- an n-p-n-p with Ga diffused into both sides of type silicon. All other diffusion procedures were an n-type silicon wafe d the an a rAu-Sn b suddenly rendered obsolete. We readily emitter alloyed on one side, was later converted the Frosch-diffused silicon n-p-n into introduce t a Generad l Electrie firsth ts a c a working p-n-p-n switch [19]." 12 Holonyak [22] noted "what Frosc Dericd han k added during the heating may be useful for revolutione basia th r t fo s hase do t n I don.s wa e protecting an electrical device from fact, it is the oxide on silicon that is the basis, the atmospheric conditions. For example, the vital foundatio f today'e no th f o sl 1al C f o chip d an , device might prove more stable if left silicon devices so critical to the electronics industry. enclose n i suc da hquart z envelope. Because of our (Holonyak) exploratory silicon possible b t Howeverno mako et y l ma eal t i , device work and our involvement with Frosch, we of the necessary electrical contacts through were close observers and witnesses of his work. For the quartz. In these cases some protection n a extensiv f L o BT e5 1 . examplep n o , ma e retaine yb e remova th a smaly db f o l l memorandum [177], Frosch wrote:" area of the envelope for the application of the contacts." "Thin silicon slices also were diffused with . HolonyaN r fo r preliminarb kfo S y device Holonya summarizes kha d Frosch's innovation development investigations. These were by "Frosch had, indeed, anticipated planar, oxide- hour6 1 d s an respectivel 5 diffuse , 2 r fo d y protected device processing e appreciateH . d at 1300°C in N2 saturated with water vapor immediatel e importancth y e oxides i th t f I o .e at room temperature. After diffusion, these questionabl f anyoni e e else's contributios a d ha n slices were green in color with an excellent o witmuce d existenc th ho e "chip t h th d f o an e" surface appearance. These layers were today's electronic Frosch's sa s oxide. Thi easils si y reporte havo dt e resistivitie o f t fro o s0 m1 see y simplb n y raisin e questionth g : Removee th 0 ohm 2 r squarepe s e diffusioTh . n layers oxide, say it doesn't exist, and then what would were reporte e uniforb o t d n thicknesmi s there Siliconbe? itself is,course,of criticalthe being 0.26, 0.39 and 0.76 mils respectively ingredient followed by its unique natural oxide. In for the 3 heating times. An additional run some sense it could its saidbe and that Si was made for Holonyak to produce layers of technology (its oxide) "invented" the 1C" (italics somewhat higher resistivity. In this run the entered by the author). thin silicon slices were heated for 1 hour at The benefits of SiO2 on the surface properties 1200°C followed by 16 hours at 1300°C in of silicon were concurrently, or shortly thereafter, N2 saturated with water vapo t a roor m assesse Attala'y db s group [11,178]. They believed temperature. These samples again were that growing an oxide under clean and controlled gree n i colon r with excellent surface conditions, on a properly cleaned silicon wafer, appearance. These were reporte o havt d e would lead to both a reduction of surface states 0 ohm 9 resistivitier squaro pe t s 5 e4 f o s and passivatio e silicoth f no n surface e planaTh . r with a diffusion depth of 0.66 mils. The diffused transistor develope Hoerny db i [12-15f o ] higher resistivity values obtained indicate Fairchild Semiconductor Corporatio e latth e n i n not only a lower solubility of the Sb 1950's pulled together a number of these strands as compoun quarte th n di z envelop t 1200°ea C regards the benefits of SiO2 and was in production than at 1300°C but also the essential by 1959. These included the concept that the SiO2 absencb compounS f o e d e th vapo n i r masking layer, e utilizefabricatioth n i d f o n carrier gas when the temperature was raised diffused silicon transistors, be left in place for the to 1300°C. Holonyak was able to produce passivation of p-n junctions intersecting the very promising cross-point switches from surfacgrowe case th th f eo nn ei junction , allod yan some of these Sb diffusions." diffused mesa transistors, without the necessity of growing a passivating oxide under meticulously Holonyak [22] continue sayiny sb knee g"w w clean condition se insigh[179]th r f Hoerno pe t, i Frosch's work at first hand, and realized [12-15] as well as ensuring a dielectric layer for immediately what he and Derick had done.